# Have You Seen The Light?

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How much do you know about the science of light and how it affects security?

• 1.

### The ____________ is the adjustment of the lens opening, which controls the amount of light allowed to pass through the lens.

• A.

Iris

• B.

Shutter speed

• C.

Glass elements

• D.

Aperture

D. Aperture
Explanation
Aperture is the correct answer because it refers to the adjustment of the lens opening. By controlling the size of the aperture, photographers can regulate the amount of light that enters the camera and reaches the image sensor. A larger aperture (smaller f-number) allows more light to pass through, resulting in a brighter image, while a smaller aperture (larger f-number) restricts the amount of light, resulting in a darker image. Therefore, aperture plays a crucial role in determining the exposure and depth of field in a photograph.

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• 2.

### Luminous flux is ____________.

• A.

Fluorescent and used to solder stained glass

• B.

The SI unit of illuminance and luminous emittance

• C.

Used in the 1985 movie “Back to the Future” to power the DeLorean

• D.

What occurs in an office when the owner is away

B. The SI unit of illuminance and luminous emittance
Explanation
The correct answer is "the SI unit of illuminance and luminous emittance". Luminous flux refers to the total amount of light energy emitted per second in all directions from a light source. It is measured in lumens (lm) and is used to quantify the brightness or intensity of light. Illuminance, on the other hand, measures the amount of light that falls on a surface per unit area, and luminous emittance measures the amount of light emitted by a surface per unit area. Both illuminance and luminous emittance are measured in lumens per square meter (lm/m²) or lux (lx), which is the SI unit for illuminance.

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• 3.

### Surfaces that are illuminated with standard daylight have an average illuminance of ____________ lux.

• A.

10,000 – 25,000

• B.

5,000

• C.

100,000

• D.

67,500

A. 10,000 – 25,000
Explanation
The correct answer is 10,000 - 25,000 lux. This range represents the average illuminance of surfaces that are illuminated with standard daylight. Lux is the unit of measurement for illuminance, which is the amount of light that falls on a surface. Standard daylight typically provides a moderate to high level of illuminance, which falls within the given range.

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• 4.

### Sodium vapor lighting generally emits a bright white light that looks like daylight.

• A.

True

• B.

False

B. False
Explanation
Sodium vapor lighting generally emits a yellowish-orange light, not a bright white light that looks like daylight.

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• 5.

### The lux is equal to ____________ lumen per square ____________.

• A.

Ten / acre

• B.

One / foot

• C.

Five / mile

• D.

One / meter

B. One / foot
Explanation
The correct answer is "one / foot" because lux is a unit of illuminance, which measures the amount of light that falls on a surface. It is equal to one lumen per square foot, meaning that one lumen of light is spread evenly over one square foot of area.

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• 6.

### Infrared lighting has a longer wavelength than visible lighting.

• A.

True

• B.

False

A. True
Explanation
Infrared lighting has a longer wavelength than visible lighting. This means that the waves of infrared light are longer and have lower frequencies compared to visible light. Infrared light is not visible to the human eye but can be detected as heat. This property makes it useful in various applications such as night vision cameras and remote controls. Therefore, the statement is true.

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• 7.

### Light is ____________ energy that is visible to the human eye.

• A.

Concave

• B.

Convex

• C.

• D.

Reflected

Explanation
Light is radiant energy that is visible to the human eye. Radiant energy refers to energy that travels in the form of electromagnetic waves, including visible light. The human eye is sensitive to this specific range of electromagnetic waves, allowing us to perceive light. Therefore, "radiant" accurately describes light as a form of energy that is visible to us.

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• 8.

### The visible light spectrum runs from ____________ nanometers.

• A.

380 – 750

• B.

100 – 450

• C.

50 – 75

• D.

1275 – 3200

A. 380 – 750
Explanation
The visible light spectrum refers to the range of wavelengths of light that can be detected by the human eye. It includes colors ranging from violet (shorter wavelength) to red (longer wavelength). The correct answer, 380 - 750 nanometers, represents the wavelengths of light that are visible to the human eye, with violet being at the lower end of the spectrum and red at the higher end.

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• 9.

### The aperture has an effect on the depth of field.

• A.

True

• B.

False

A. True
Explanation
The aperture refers to the opening in the lens through which light enters the camera. It plays a crucial role in determining the depth of field in a photograph. A wider aperture (smaller f-number) results in a shallow depth of field, where only a small portion of the image is in focus, while the rest appears blurred. On the other hand, a narrower aperture (larger f-number) increases the depth of field, making more of the image appear sharp and in focus. Therefore, it is correct to say that the aperture has an effect on the depth of field.

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• 10.

### The “glow” from infrared lighting sources typically can not be seenat ranges starting at about ____________ nanometers.

• A.

380 – 700

• B.

650 – 700

• C.

700 – 900

• D.

900 – 1000

D. 900 – 1000
Explanation
Infrared lighting sources emit light with longer wavelengths than visible light. The range of infrared light that is typically not visible to the human eye starts at around 900 nanometers and goes up to 1000 nanometers. This means that any light emitted by infrared lighting sources within this range will not be perceived as a visible glow.

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• 11.

### To keep an image sharp, which of the following lens types is the proper one to use when a camera must switch from visible light to infrared light viewing?

• A.

Multi-element

• B.

Spherical

• C.

Auto iris

• D.

Aspherical

D. Aspherical
Explanation
Aspherical lenses are the proper lens type to use when a camera needs to switch from visible light to infrared light viewing in order to keep the image sharp. Aspherical lenses have a more complex shape compared to spherical lenses, which helps to reduce optical aberrations and distortions. This makes them ideal for capturing clear and sharp images, even when switching between different types of light.

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• 12.

### A Fresnel lens can typically be seen in ____________.

• A.

A color IP camera

• B.

Standard CCTV cameras

• C.

CCTV cameras with built in auto iris

• D.

A motion detector

D. A motion detector
Explanation
A Fresnel lens can typically be seen in a motion detector because it is used to focus and direct the light onto the sensor, allowing the motion detector to accurately detect any movement within its range. The Fresnel lens helps to enhance the sensitivity and effectiveness of the motion detector by capturing and concentrating the incoming light. This allows the motion detector to accurately detect any changes in the light patterns, triggering an alarm or activating the desired response.

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• 13.

### CIF is short for ____.

• A.

Commercial Industrial Format

• B.

Camera Identification Frame

• C.

Common Intermediate Format

• D.

Compressed Indexed Frame

C. Common Intermediate Format
Explanation
The correct answer is Common Intermediate Format. CIF is a video resolution standard used in videoconferencing and surveillance systems. It has a resolution of 352x288 pixels and a 4:3 aspect ratio. The term "common" refers to its widespread use, while "intermediate" indicates that it is a compromise between higher and lower resolutions. This format is commonly used for video compression and transmission in various applications.

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• 14.

### The larger the f-stop number, the larger the depth of field.

• A.

True

• B.

False

A. True
Explanation
The f-stop number refers to the aperture setting on a camera lens. A larger f-stop number means a smaller aperture, which in turn increases the depth of field. This means that more of the image, both near and far, will be in focus. Therefore, the statement is true.

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• 15.

### One foot-candle is equal to one lumen per square foot or approximately ____________ lux.

• A.

10.764

• B.

1

• C.

36

• D.

144

A. 10.764
Explanation
One foot-candle is a unit of measurement for illuminance, which is the amount of light that falls on a surface. It is equal to one lumen per square foot. The correct answer, 10.764, is the conversion factor from foot-candles to lux. Lux is the SI unit for illuminance and is equal to one lumen per square meter. Therefore, to convert foot-candles to lux, you would multiply the foot-candle value by 10.764.

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• Mar 06, 2024
Quiz Edited by
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• Nov 17, 2014
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