Question

How much energy does a photon of UV light (frequency = 3.6 x 10^6 Hz) have? How fast does the light
travel in vaccum, water (n=1.33), and glass (n=1.50)?​

Answer 1

Given - Frequency of photon of UV light - 3.6 x 10^6 Hz

Refractive index of water - 1.33 and refractive index of glass - 1.50

Find - Energy of photon of UV light Nd speed of light in vaccum, water and glass.

Solution - Energy of photon can be calculated by the formula E - h*f, where E is energy, h is Planck's constant and f is frequency.

Keeping the values in equation-

E - 6.626 x 10–³⁴*3.6 x 10⁶

E - 2.38*10-²⁷ J.

Light travels in vaccum with the speed of 3*10⁸ m/s.

Speed of light in glass and water can be calculated by the formula - n - c/v, where n is refractive index, c is speed of light in vaccum and v is speed of light in another medium.

Keeping the values in equation-

v(water) - 3*10⁸/1.33

speed of light in water - 2.25*10⁸ m/s.

Similarly, speed of light in glass - 2*10⁸ m/s.