# Chapter 23: Light: Geometric Optics

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• 1.

### Reflection, refraction, and the formation of images by mirrors and lenses has been successful described by the

• A.

Wave model of light.

• B.

Ray model of light.

• C.

Particle model of light.

• D.

B. Ray model of light.
Explanation
The correct answer is the ray model of light. This model explains how light travels in straight lines called rays, and how it interacts with mirrors and lenses through reflection and refraction. It does not consider light as a wave or a particle, but rather as a stream of rays that can be traced to understand its behavior.

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• 2.

### The angle of incidence

• A.

Must equal the angle of reflection.

• B.

Is always less than the angle of reflection.

• C.

Is always greater than the angle of reflection.

• D.

May be greater than, less than, or equal to the angle of reflection.

A. Must equal the angle of reflection.
Explanation
The statement "The angle of incidence must equal the angle of reflection" is based on the law of reflection, which states that when a ray of light reflects off a surface, the angle of incidence (the angle between the incident ray and the normal to the surface) is equal to the angle of reflection (the angle between the reflected ray and the normal to the surface). This law applies to all types of reflections, whether it is light reflecting off a mirror, water surface, or any other reflective surface. Therefore, the angle of incidence must always be equal to the angle of reflection.

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• 3.

### The principle on which mirrors work is

• A.

Refraction.

• B.

Polarization.

• C.

Dispersion.

• D.

Reflection.

D. Reflection.
Explanation
Mirrors work based on the principle of reflection. When light hits the surface of a mirror, it bounces off in a predictable way, allowing us to see our reflection. This is because mirrors have a smooth and highly reflective surface that causes light to reflect back in a straight line. Refraction, polarization, and dispersion are not the principles on which mirrors work. Refraction refers to the bending of light as it passes through different mediums, polarization refers to the alignment of light waves, and dispersion refers to the separation of light into its different colors.

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• 4.

### A plane mirror forms an image that is

• A.

Real and upright.

• B.

Virtual and upright.

• C.

Real and upside down.

• D.

Virtual and upside down.

B. Virtual and upright.
Explanation
A plane mirror forms a virtual image because the light rays do not actually converge or meet at the location of the image. Instead, the image appears to be behind the mirror, which makes it virtual. The image formed by a plane mirror is also upright because the top and bottom of the object are reflected in the same orientation as the original object.

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• 5.

### Plane mirrors produce images which

• A.

Are always smaller than the actual object.

• B.

Are always larger than the actual object.

• C.

Are always the same size as the actual object.

• D.

Could be smaller, larger, or the same size as the actual object, depending on the placement of the object.

C. Are always the same size as the actual object.
Explanation
Plane mirrors produce images that are always the same size as the actual object. This is because plane mirrors reflect light rays in a way that preserves the size and shape of the object being reflected. The image formed in a plane mirror appears to be behind the mirror, but it is not actually smaller or larger than the object. The image is a virtual image, meaning it cannot be projected onto a screen, and it appears to be the same distance behind the mirror as the object is in front of it.

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• 6.

### An image formed when the light rays do not actually pass through the image location, and would not appear on paper or film placed at that location is referred to as a

• A.

Real image.

• B.

Virtual image.

B. Virtual image.
Explanation
A virtual image is formed when the light rays do not actually pass through the image location and would not appear on paper or film placed at that location. It is a result of the apparent intersection of light rays when they are projected backwards from the lens or mirror. Unlike a real image, a virtual image cannot be captured on a screen or surface as it only exists in the perception of the observer.

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• 7.

### An image formed when the light rays pass through the image location, and could appear on paper or film placed at the that location is referred to as a

• A.

Real image.

• B.

Virtual image.

A. Real image.
Explanation
A real image is formed when light rays converge at a specific location after passing through an object. This image can be captured on a screen or film, as it exists in physical space. In contrast, a virtual image is formed when light rays appear to come from a specific location but do not actually converge there. Therefore, the correct answer is real image.

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• 8.

### Is it possible to see a virtual image?

• A.

No, since the rays that seem to emanate from a virtual image do not in fact emanate from the image.

• B.

No, since virtual images do not really exist.

• C.

Yes, the rays that appear to emanate from a virtual image can be focused on the retina just like those from an illuminated object.

• D.

Yes, since almost everything we see is virtual because most things do not themselves give off light, but only reflect light coming from some other source.

• E.

Yes, but only indirectly in the sense that if the virtual image is formed on a sheet of photographic film, one could later look at the picture formed.

C. Yes, the rays that appear to emanate from a virtual image can be focused on the retina just like those from an illuminated object.
Explanation
Yes, the rays that appear to emanate from a virtual image can be focused on the retina just like those from an illuminated object. This is possible because the human eye cannot distinguish between the rays of light that come from a real object and those that appear to come from a virtual image. The retina receives these rays and processes them as if they were coming from a physical object, allowing us to perceive the virtual image as if it were real.

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• 9.

### A spherical mirror on which reflection takes place on the outer surface of the spherical shape is referred to as a

• A.

Convex mirror.

• B.

Concave mirror.

A. Convex mirror.
Explanation
A convex mirror is a spherical mirror on which reflection takes place on the outer surface of the spherical shape. This type of mirror curves outward, causing light rays to diverge. It is commonly used in applications such as side-view mirrors in vehicles and security mirrors in stores. The reflection in a convex mirror results in a smaller, virtual, and upright image.

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• 10.

### A spherical mirror on which reflection takes place on the inner surface of the sphere is referred to as a

• A.

Convex mirror.

• B.

Concave mirror.

B. Concave mirror.
Explanation
A concave mirror is a spherical mirror on which reflection takes place on the inner surface of the sphere. In a concave mirror, the reflecting surface curves inward, causing light rays to converge at a focal point. This type of mirror is commonly used in telescopes and headlights, as it can form real and inverted images. On the other hand, a convex mirror has a reflecting surface that curves outward, causing light rays to diverge. Convex mirrors are commonly used in rear-view mirrors and security mirrors, as they provide a wider field of view but produce virtual and upright images.

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• 11.

### If the radius of curvature of the concave mirror is r, the focal length is

• A.

2r.

• B.

R.

• C.

R/2.

• D.

Cannot be determined from the information given

C. R/2.
Explanation
The focal length of a concave mirror is half of its radius of curvature. Therefore, if the radius of curvature is r, the focal length will be r/2.

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• 12.

### A light ray, traveling parallel to a concave mirror's axis, strikes the mirror's surface near its midpoint. After reflection, this ray

• A.

Again travels parallel to the mirror's axis.

• B.

Travels at right angles to the mirror's axis.

• C.

Passes through the mirror's center of curvature.

• D.

Passes through the mirror's focal point.

D. Passes through the mirror's focal point.
Explanation
When a light ray traveling parallel to the concave mirror's axis strikes the mirror's surface near its midpoint, it will be reflected in such a way that it passes through the mirror's focal point. This is a property of concave mirrors known as the "law of reflection." The focal point is the point on the principal axis where light rays parallel to the axis converge or appear to diverge from after reflection. Therefore, the correct answer is that the ray passes through the mirror's focal point.

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• 13.

### Light arriving at a concave mirror on a path parallel to the axis is reflected

• A.

Back parallel to the axis.

• B.

Back on itself.

• C.

Through the focal point.

• D.

Through the center of curvature.

C. Through the focal point.
Explanation
When light rays parallel to the axis of a concave mirror hit the mirror's surface, they reflect and converge at a point known as the focal point. This is because a concave mirror is curved inward, causing the light rays to converge towards a point. Therefore, the correct answer is that the light is reflected through the focal point.

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• 14.

### A light ray, traveling obliquely to a concave mirror's axis, crosses the axis at the mirror's center of curvature before striking the mirror's surface. After reflection, this ray

• A.

Travels parallel to the mirror's axis.

• B.

Travels at right angles to the mirror's axis.

• C.

Passes through the mirror's center of curvature.

• D.

Passes through the mirror's focal point.

C. Passes through the mirror's center of curvature.
Explanation
When a light ray traveling obliquely to a concave mirror's axis crosses the axis at the mirror's center of curvature, it undergoes reflection. According to the laws of reflection, the angle of incidence is equal to the angle of reflection. Since the light ray crosses the axis at the center of curvature, the angle of incidence is 0 degrees. Therefore, the angle of reflection is also 0 degrees, causing the reflected ray to pass through the mirror's center of curvature.

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• 15.

### Light arriving at a concave mirror on a path through the center of curvature is reflected

• A.

Back parallel to the axis.

• B.

Back on itself.

• C.

Through the focal point.

• D.

Midway between the focal point and the center of curvature.

B. Back on itself.
Explanation
When light rays pass through the center of curvature of a concave mirror, they strike the mirror perpendicularly. According to the law of reflection, the angle of incidence is equal to the angle of reflection. Since the light rays are incident at a 90-degree angle, they reflect back along the same path, resulting in the light "backing on itself." This phenomenon occurs because the center of curvature is the point on the mirror where the radius of curvature intersects the mirror's surface.

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• 16.

### A light ray, traveling obliquely to a concave mirror's surface, crosses the axis at the mirror's focal point before striking the mirror's surface. After reflection, this ray

• A.

Travels parallel to the mirror's axis.

• B.

Travels at right angles to the mirror's axis.

• C.

Passes through the mirror's center of curvature.

• D.

Passes through the mirror's focal point.

A. Travels parallel to the mirror's axis.
Explanation
When a light ray travels obliquely to a concave mirror's surface and crosses the axis at the mirror's focal point, it follows the law of reflection. According to this law, the angle of incidence is equal to the angle of reflection. In the case of a concave mirror, the focal point is located on the mirror's axis. As the light ray crosses the axis at the focal point, it will reflect back parallel to the axis. This is because the angle of incidence is equal to the angle of reflection, resulting in a parallel path to the mirror's axis.

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• 17.

### Light arriving at a concave mirror on a path through the focal point is reflected

• A.

Back parallel to the axis.

• B.

Back on itself.

• C.

Through the focal point.

• D.

Through the center of curvature.

A. Back parallel to the axis.
Explanation
When light rays arrive at a concave mirror on a path through the focal point, they will be reflected back parallel to the axis. This is due to the unique shape of the concave mirror, which causes the reflected rays to converge at the focal point. Since the incident rays are already passing through the focal point, they will be reflected in a way that they continue on a path parallel to the axis of the mirror.

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• 18.

### If you stand in front of a concave mirror, exactly at its focal point,

• A.

You won't see your image because there is none.

• B.

You won't see your image because it's focused at a different distance.

• C.

You will see your image, and you will appear smaller.

• D.

You will see your image and you will appear larger.

• E.

A. You won't see your image because there is none.
Explanation
When standing exactly at the focal point of a concave mirror, the light rays that would form an image are parallel and do not converge. As a result, there is no image formed and therefore, you won't see your image.

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• 19.

### An object is placed at a concave mirror's center of curvature. The image produced by the mirror is located

• A.

Out beyond the center of curvature.

• B.

At the center of curvature.

• C.

Between the center of curvature and the focal point.

• D.

At the focal point.

B. At the center of curvature.
Explanation
When an object is placed at the center of curvature of a concave mirror, the image produced by the mirror is located at the center of curvature. This is because the rays of light coming from the object are reflected back parallel to each other, resulting in an image that is formed at the same distance behind the mirror as the object is placed in front of it. Therefore, the correct answer is "at the center of curvature."

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• 20.

### An object is positioned between a concave mirror's center of curvature and its focal point. The image produced by the mirror is located

• A.

Out past the center of curvature.

• B.

At the center of curvature.

• C.

Between the center of curvature and the focal point.

• D.

At the focal point.

A. Out past the center of curvature.
Explanation
When an object is positioned between the center of curvature and the focal point of a concave mirror, the image produced is located out past the center of curvature. This is because in this position, the mirror forms a virtual and magnified image on the same side as the object. The image is formed by the reflected rays converging after they pass through the focal point, resulting in an image that is further away from the mirror than the center of curvature.

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• 21.

### An object is situated between a concave mirror's surface and its focal point. The image formed in this case is

• A.

Real and inverted.

• B.

Real and erect.

• C.

Virtual and erect.

• D.

Virtual and inverted.

C. Virtual and erect.
Explanation
When an object is situated between a concave mirror's surface and its focal point, the image formed is virtual and erect. In this case, the rays of light from the object diverge after reflecting from the mirror, and they appear to meet at a point behind the mirror. The image formed is virtual because it cannot be projected onto a screen, and it is erect because it appears upright compared to the object.

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• 22.

### If you stand in front of a convex mirror, at the same distance from it as its radius of curvature,

• A.

You won't see your image because there is none.

• B.

You won't see your image because it's focused at a different distance.

• C.

You will see your image and you will appear smaller.

• D.

You will see your image and you will appear larger.

• E.

C. You will see your image and you will appear smaller.
Explanation
When standing in front of a convex mirror at the same distance from it as its radius of curvature, the image formed will be virtual and smaller in size compared to the actual object. This is because convex mirrors always produce virtual images that are diminished in size. The image appears smaller because the diverging rays of light from different points on the object are reflected in such a way that they appear to originate from a point behind the mirror, resulting in a smaller image.

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• 23.

### If you stand in front of a convex mirror, at the same distance from it as its focal length,

• A.

You won't see your image because there is none.

• B.

You won't see your image because it's focused at a different distance.

• C.

You will see your image and you will appear smaller.

• D.

You will see your image and you will appear larger.

• E.

C. You will see your image and you will appear smaller.
Explanation
When you stand in front of a convex mirror at the same distance from it as its focal length, you will see your image, but it will appear smaller. This is because convex mirrors always produce virtual and diminished images. The convex shape of the mirror causes light rays to diverge, resulting in the formation of a smaller image.

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• 24.

### Sometimes when you look into a curved mirror you see a magnified image (a great big you) and sometimes you see a diminished image (a little you). If you look at the bottom (convex) side of a shiny spoon, what will you see?

• A.

You won't see an image of yourself because no image will be formed.

• B.

You will see a little you, upside down.

• C.

You will see a little you, right side up.

• D.

You will see a little you, but whether you are right side up or upside down depends on how near you are to the spoon.

• E.

You will either see a little you or a great big you, epending on how near you are to the spoon.

C. You will see a little you, right side up.
Explanation
When looking at the bottom (convex) side of a shiny spoon, the image formed is a virtual image. This means that the light rays do not actually converge to form a real image. Instead, the light rays appear to diverge from a point behind the mirror. In the case of a convex mirror, the virtual image formed is always smaller and right side up. Therefore, when looking at the bottom side of a shiny spoon, you will see a little you, right side up.

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• 25.

### Concave spherical mirrors produce images which

• A.

Are always smaller than the actual object.

• B.

Are always larger than the actual object.

• C.

Are always the same size as the actual object.

• D.

Could be smaller than, larger than, or the same size as the actual object, depending on the placement of the object.

D. Could be smaller than, larger than, or the same size as the actual object, depending on the placement of the object.
Explanation
Concave spherical mirrors can produce images that are smaller, larger, or the same size as the actual object depending on the placement of the object. This is because concave mirrors have a curved surface that can cause the light rays to converge or diverge, leading to different image sizes. When the object is placed beyond the focal point of the mirror, the image is smaller. When the object is placed between the focal point and the mirror, the image is larger. And when the object is placed at the focal point, the image is the same size as the object. Therefore, the size of the image can vary depending on the placement of the object.

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• 26.

### Convex spherical mirrors produce images which

• A.

Are always smaller than the actual object.

• B.

Are always larger than the actual object.

• C.

Are always the same size as the actual object.

• D.

Could be larger than, smaller than, or the same size as the actual object, depending on the placement of the object.

A. Are always smaller than the actual object.
Explanation
Convex spherical mirrors are characterized by their outward curved shape. When an object is placed in front of a convex mirror, the light rays from the object diverge after reflection. This divergence causes the image formed by the mirror to appear smaller than the actual object. Therefore, convex spherical mirrors always produce images that are smaller than the actual object.

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• 27.

### A single concave spherical mirror produces an image which is

• A.

Always virtual.

• B.

Always real.

• C.

Real only if the object distance is less than f.

• D.

Real only if the object distance is greater than f.

D. Real only if the object distance is greater than f.
Explanation
A single concave spherical mirror produces an image that is real only if the object distance is greater than the focal length (f). This is because a concave mirror focuses light rays that are parallel to its principal axis at a point called the focal point. When the object distance is greater than the focal length, the image is formed on the same side as the object and is real. However, when the object distance is less than the focal length, the image is formed on the opposite side of the mirror and is virtual.

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• 28.

### A single convex spherical mirror produces an image which is

• A.

Always virtual.

• B.

Always real.

• C.

Real only if the object distance is less than f.

• D.

Real only if the object distance is greater than f.

A. Always virtual.
Explanation
A single convex spherical mirror produces an image which is always virtual because the image formed by a convex mirror is always upright, diminished in size, and located behind the mirror. The rays of light that reflect off the mirror diverge, rather than converge, which results in the formation of a virtual image. This is in contrast to a concave mirror, which can produce both real and virtual images depending on the position of the object relative to the focal point.

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• 29.

### A negative magnification for a mirror means

• A.

The image is inverted, and the mirror is concave.

• B.

The image is inverted, and the mirror is convex.

• C.

The image is inverted, and the mirror may be concave or convex.

• D.

The image is upright, and the mirror is convex.

• E.

The image is upright, and the mirror may be concave or convex.

A. The image is inverted, and the mirror is concave.
Explanation
A negative magnification for a mirror means that the image formed by the mirror is inverted. Additionally, the fact that the mirror is concave is also indicated by the negative magnification.

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• 30.

### If the image distance is positive, the image formed is a

• A.

Real image.

• B.

Virtual image.

A. Real image.
Explanation
When the image distance is positive, it means that the image is formed on the opposite side of the lens or mirror from the object. In this case, the light rays converge to a point after passing through the lens or reflecting off the mirror, creating a real image. A real image can be projected onto a screen and is formed by the actual intersection of light rays.

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• 31.

### If the image distance is negative, the image formed is a

• A.

Real image.

• B.

Virtual image.

B. Virtual image.
Explanation
If the image distance is negative, it means that the image is formed on the same side as the object. In this case, a virtual image is formed. A virtual image is formed when the light rays do not actually converge at a point, but appear to diverge from a point behind the mirror or lens. It cannot be projected onto a screen and is always upright.

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• 32.

### If the magnification is a positive value, the image is

• A.

Upright.

• B.

Inverted.

A. Upright.
Explanation
If the magnification is a positive value, it means that the image is larger than the object. In this case, the image appears upright because the light rays are converging and forming a real image on the same side as the object. This is typically observed in magnifying glasses or convex lenses.

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• 33.

### If the magnification is a negative value, the image is

• A.

Upright.

• B.

Inverted.

B. Inverted.
Explanation
If the magnification is a negative value, it indicates that the image is formed on the opposite side of the lens compared to the object. This means that the image is inverted, as the top of the object will appear at the bottom of the image and vice versa.

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• 34.

### If the absolute value of the magnification is larger than one, then the image is

• A.

Larger than the object.

• B.

The same size as the object.

• C.

Smaller than the object.

A. Larger than the object.
Explanation
If the absolute value of the magnification is larger than one, it means that the image is enlarged compared to the object. This is because the magnification represents the ratio of the size of the image to the size of the object. A magnification greater than one indicates that the image is larger than the object.

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• 35.

### If the absolute value of the magnification is smaller than one, then the image is

• A.

Larger than the object.

• B.

The same size as the object.

• C.

Smaller than the object.

C. Smaller than the object.
Explanation
If the absolute value of the magnification is smaller than one, it means that the image is smaller than the object. This is because magnification refers to the ratio of the size of the image to the size of the object. A magnification smaller than one indicates that the image is reduced in size compared to the object.

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• 36.

### If the absolute value of the magnification is equal to one, then the image is

• A.

Larger than the object.

• B.

The same size as the object.

• C.

Smaller than the object.

B. The same size as the object.
Explanation
If the absolute value of the magnification is equal to one, it means that the image is neither magnified nor reduced in size. It is exactly the same size as the object.

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• 37.

### Light travels fastest

• A.

In a vacuum.

• B.

Through water.

• C.

Through glass.

• D.

Through diamond.

A. In a vacuum.
Explanation
Light travels fastest in a vacuum because a vacuum is a space devoid of any matter or particles. In other mediums like water, glass, or diamond, light encounters particles and molecules that can interact with it, causing it to slow down. However, in a vacuum, there are no particles to impede its motion, allowing light to travel at its maximum speed.

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• 38.

### For all transparent material substances, the index of refraction

• A.

Is less than 1.

• B.

Is greater than 1.

• C.

Is equal to 1.

• D.

Could be any of the given answers; it all depends on optical density.

B. Is greater than 1.
Explanation
The index of refraction is a measure of how much light is bent when passing through a material. It is defined as the ratio of the speed of light in a vacuum to the speed of light in the material. Since the speed of light is always less than the speed of light in a vacuum when passing through a material, the index of refraction is always greater than 1.

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• 39.

### An index of refraction less than one for a medium would imply

• A.

That the speed of light in the medium is the same as the speed of light in vacuum.

• B.

That the speed of light in the medium is greater than the speed of light in vacuum.

• C.

Refraction is not possible.

• D.

Reflection is not possible.

B. That the speed of light in the medium is greater than the speed of light in vacuum.
Explanation
An index of refraction less than one indicates that the speed of light in the medium is greater than the speed of light in a vacuum. This is because the index of refraction is defined as the ratio of the speed of light in a vacuum to the speed of light in the medium. When the index of refraction is less than one, it means that the speed of light in the medium is higher than in a vacuum.

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• 40.

### The index of refraction of diamond is 2.42. This means that a given frequency of light travels

• A.

2.42 times faster in air than it does in diamond.

• B.

2.42 times faster in diamond than it does in air.

• C.

2.42 times faster in vacuum than it does in diamond.

• D.

2.42 times faster in diamond than it does in vacuum.

C. 2.42 times faster in vacuum than it does in diamond.
Explanation
The correct answer is "2.42 times faster in vacuum than it does in diamond." The index of refraction measures how much slower light travels in a medium compared to its speed in a vacuum. Since the index of refraction of diamond is 2.42, it means that light travels 2.42 times slower in diamond than it does in vacuum. Therefore, the given frequency of light will travel 2.42 times faster in vacuum than it does in diamond.

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• 41.

### The angle of incidence

• A.

Must equal the angle of refraction.

• B.

Is always less than the angle of refraction.

• C.

Is always greater than the angle of refraction.

• D.

May be greater than, less than, or equal to the angle of refraction.

D. May be greater than, less than, or equal to the angle of refraction.
Explanation
The angle of incidence refers to the angle at which a ray of light or a wave hits a surface. The angle of refraction, on the other hand, refers to the angle at which the ray of light or wave bends or changes direction when it passes from one medium to another. The relationship between the angle of incidence and the angle of refraction is described by Snell's law, which states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to a constant value. This means that the angle of incidence can be greater than, less than, or equal to the angle of refraction, depending on the properties of the media involved. Therefore, the correct answer is that the angle of incidence may be greater than, less than, or equal to the angle of refraction.

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• 42.

### Light traveling at an angle into a denser medium is refracted

• A.

Toward the normal.

• B.

Away from the normal.

• C.

Parallel to the normal.

• D.

Equally.

A. Toward the normal.
Explanation
When light travels from a less dense medium to a denser medium, such as from air to water, it changes direction. This change in direction is known as refraction. The angle at which the light ray enters the denser medium is called the angle of incidence, and the angle at which it bends is called the angle of refraction. According to the laws of refraction, when light enters a denser medium at an angle, it bends towards the normal, which is an imaginary line perpendicular to the surface of the medium. Therefore, the correct answer is "toward the normal."

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• 43.

### Light enters air from water. The angle of refraction will be

• A.

Greater than the angle of incidence.

• B.

Equal to the angle of incidence.

• C.

Less than the angle of incidence.

A. Greater than the angle of incidence.
Explanation
When light travels from a medium with a higher refractive index (water) to a medium with a lower refractive index (air), it undergoes refraction. According to Snell's law, the angle of refraction is determined by the ratio of the refractive indices of the two media. Since the refractive index of water is higher than that of air, the angle of refraction will be greater than the angle of incidence. Therefore, the correct answer is "greater than the angle of incidence."

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• 44.

### A ray of light, which is traveling in air, is incident on a glass plate at a 45° angle. The angle of refraction in the glass

• A.

Is less than 45°.

• B.

Is greater than 45°.

• C.

Is equal to 45°.

• D.

Could be any of the above; it all depends on the index of refraction of glass.

A. Is less than 45°.
Explanation
When a ray of light travels from a medium with a lower refractive index (such as air) to a medium with a higher refractive index (such as glass), it bends towards the normal (an imaginary line perpendicular to the surface of the glass). This bending is known as refraction. According to Snell's law, the angle of refraction is determined by the refractive indices of the two media and the angle of incidence. Since the angle of incidence is 45°, and the refractive index of glass is higher than that of air, the ray of light will bend towards the normal, resulting in an angle of refraction that is less than 45°.

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• 45.

### The principle on which fiber optics is based is

• A.

Refraction.

• B.

Polarization.

• C.

Dispersion.

• D.

Total internal reflection.

D. Total internal reflection.
Explanation
Fiber optics is based on the principle of total internal reflection. This occurs when light traveling through a medium with a higher refractive index encounters a boundary with a medium of lower refractive index at an angle greater than the critical angle. In this case, the light is completely reflected back into the medium with higher refractive index, instead of being refracted out. This principle is used in fiber optic cables, where light signals are transmitted through a core of high refractive index material, surrounded by a cladding of lower refractive index material, allowing for efficient transmission of light signals over long distances.

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• 46.

### The critical angle for a beam of light passing from water into air is 48.8°. This means that all light rays with an angle of incidence greater than this angle will be

• A.

Absorbed

• B.

Totally reflected.

• C.

Partially reflected and partially transmitted.

• D.

Totally transmitted.

B. Totally reflected.
Explanation
When a beam of light passes from a medium with a higher refractive index to a medium with a lower refractive index, there is a critical angle at which the light is no longer refracted but instead undergoes total internal reflection. In this case, the critical angle is given as 48.8°. This means that any light ray with an angle of incidence greater than 48.8° will not be transmitted into the air but will be reflected back into the water. Therefore, the correct answer is "totally reflected."

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• 47.

### The principle on which lenses work is

• A.

Refraction.

• B.

Polarization.

• C.

Dispersion.

• D.

Total internal reflection.

A. Refraction.
Explanation
Lenses work based on the principle of refraction, which is the bending of light as it passes through a different medium. When light enters a lens, it changes direction due to the change in speed caused by the change in medium. This bending of light allows lenses to focus or diverge light, resulting in various optical effects such as magnification, image formation, and correction of vision problems. Refraction is the fundamental principle behind the functioning of lenses in various optical devices like cameras, microscopes, telescopes, and eyeglasses.

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• 48.

### Lenses that are thickest at the center called

• A.

Converging lenses.

• B.

Diverging lenses.

A. Converging lenses.
Explanation
Converging lenses are thickest at the center and are designed to bring parallel light rays together to a single focal point. This type of lens is commonly used in magnifying glasses, telescopes, and cameras to focus light and create clear images. Diverging lenses, on the other hand, are thinnest at the center and cause parallel light rays to spread out. They are used in devices such as eyeglasses to correct nearsightedness or farsightedness.

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• 49.

### Lenses that are thinner at the center than the edges are called

• A.

Converging lenses.

• B.

Diverging lenses.

B. Diverging lenses.
Explanation
Lenses that are thinner at the center than the edges are called diverging lenses. This is because diverging lenses cause light rays to spread out or diverge after passing through them. The shape of these lenses causes the light rays to bend away from the principal axis, resulting in a virtual image that is smaller and upright. Diverging lenses are commonly used in glasses for people with nearsightedness, as they help to correct the vision by causing the light rays to spread out before entering the eye.

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• 50.

### Lenses that are thicker at the center

• A.

• B.

Bend light rays to a point beyond the lens.

• C.

Have no effect on light rays.

• D.

Reflect light rays back.

B. Bend light rays to a point beyond the lens.
Explanation
Lenses that are thicker at the center are convex lenses. Convex lenses are designed to bend light rays towards a point beyond the lens, known as the focal point. This bending of light rays is due to the curvature of the lens, causing the light rays to converge. Therefore, the correct answer is that lenses that are thicker at the center bend light rays to a point beyond the lens.

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• Current Version
• Mar 21, 2023
Quiz Edited by
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• Nov 07, 2012
Quiz Created by
Drtaylor

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