Human vision and function/Part 1: How the eye works/1.1 What is light?/Answers

1. How can you best define “light”?

It is a small component of the energy spectrum of electromagnetic radiation.

2. Which wavelengths of light are visible to the human eye?

The visible spectrum ranges from about 400nm (violet) to 800 nm (red) light.

3. Does the speed of light change depending on the wavelength it emits?

No, the speed of light remains constant, irrespective of wavelength.

4. What is the main difference between the wave theory of light compared with the quantum theory?

The wave theory states that light emitted from an object travels in waves away from that object whilst the quantum theory states that light is a packet of energy (photon) which travels in a straight line.

5. When we look at a coloured object, for example a red apple, why does it appear red?

Because the apple absorbs all light frequencies except red and red is reflected off its surface.

6. What is refraction of light?

That is when light bends as it passes through a medium such as water or our eyes.

7. Define constructive and destructive interference of waves.

''Constructive interference is when the amplitude of a wave is increased because peaks of the wave meets with peaks of the other wave and troughs meet with troughs. This causes an increase in the amplitude of the wave. Destructive interference is when peaks meet troughs and the amplitude of the wave reduces.''

8. What is the “photoelectric effect”?

The ability of light (photons) to dislodge electrons from a metal surface.