Em Spectrum - Visible Light

Explanation
The statement "Red has the shortest wavelength" is false. In the visible light spectrum, red light has the longest wavelength, while violet light has the shortest wavelength. The order of the visible light spectrum from longest to shortest wavelength is: red, orange, yellow, green, blue, indigo, and violet.

Explanation
The statement "Violet has the longest wavelength" is incorrect. In the visible light spectrum, violet light actually has the shortest wavelength. The colors in the visible light spectrum are arranged in increasing order of wavelength, with red having the longest wavelength and violet having the shortest.

Explanation
The statement "When all the waves are seen together, they make black light" is incorrect. When all the waves are seen together, they make white light, not black light. White light is a combination of all visible colors of light, while black light is the absence of light or the complete absence of any color.

Explanation
Visible light rays can be seen by the naked eye. Visible light refers to the range of electromagnetic radiation that is visible to humans. It includes the colors of the rainbow, such as red, orange, yellow, green, blue, indigo, and violet. These colors can be seen by the naked eye when light enters the eye and is detected by the photoreceptor cells in the retina. Therefore, the statement that visible light rays cannot be seen by the naked eye is false.

Explanation
The spectrum refers to the range of colors that are visible to the human eye when white light is passed through a prism. This range consists of seven colors: red, orange, yellow, green, blue, indigo, and violet. Therefore, the correct answer is 7.