Light is a form of energy which travels in the form of waves. The path of light is called a ray of light and a group of rays is called a beam of light. Sources that emit their own light are luminous objects (all the stars, including the Sun). This chapter covers refraction, dispersion and scattering of light, lenses, the human eye, microscopes and telescopes.
1. Properties of Light
- Light is a form of energy.
- Light always travels along a straight line.
- Light does not need any medium for its propagation; it can even travel through vacuum.
- The speed of light in vacuum or air is c = 3 × 10^8 m/s.
- Being waves, light is characterised by a wavelength (λ) and a frequency (ν), related by c = ν λ (c – velocity of light).
- Among visible light, violet has the lowest wavelength and red has the highest wavelength.
- At the interface of two media, light is partly reflected and partly refracted.