Question

Red light has wavelength 750nm, whereas violet light has wavelength 400nm.Calculate their

frequency and energy. (c = 3 x 108 m/s , h = 6.626 x 10-34 J s )​

Answer 1

Given:

Red light has wavelength 750nm, whereas violet light has wavelength 400nm.

To find:

Calculate their  frequency and energy.

Solution:

From given, we have,

Formula used to calculate frequency is ν = c/λ  

For red light given λ = 750nm = 7.5 ×10 -7 m  

Putting the value of λ and c in formula

ν = c/λ we get 3× 10^{8}ms-1 / 7.5 ×10 -7 m

f = 4 × 10^{14} Hz

Energy can be calculated by using formula E= hν  = 6.63 × 10-34Js  × 4.0 × 1014s-1.

E = 2.65 × 10^{-20} J

Similarly for violet light,

ν = c/λ ,

3 × 10{8}ms-1 / 4.0 × 10 -7 m

f = 7.5 × 10^{14} Hz

Energy can be calculated by using formula

E = hν  = 6.63 × 10-34Js  × 7.5 × 10^{14}s-1.

E = 4.97 × 10^{-20} J