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# Chapter 9, End of Chapter, Review Questions,Exercise 1

### Explanation

The electromagnetic spectrum consists of wavelengths, or frequencies of electromagnetic radiation varying from the gamma waves that are the shortest to the radio waves that are the longest. The light that helps in a normal vision is the visible light. Hence, visible light is a portion of the electromagnetic spectrum that can be detected by the human eye. Each color has a different spectrum in the visible range. The colors are violet, indigo, blue, green, yellow, orange, and red.

The properties of light are: frequency, wavelength, and amplitude.

1. Frequency: The number of waves of visible light passing through a given point per second is called frequency. The unit of frequency is Hertz. The frequency of the visible range is 430-790 THz. There is a decrease in the frequency from violet to red color of the spectrum.

2. Wavelength: The distance between the two consecutive points in a wave is called wavelength. The visible range for the human eye includes wavelengths between 380 and 750 nm. There is an increase in wavelength from violet to red in the visible spectrum. Greater the wavelength lower is the energy.

3. Amplitude: The brightness of light is known as amplitude. It is the difference between wave trough and peak. A greater amplitude indicates greater intensity and brightness of light. A brighter light is easily detectable by the eye compared to dull light.