Question

K.E. of photo electrons ______ on doubling frequency of incident light.

• A. triple
• B. double
• C. become half
• D. quadrupled

Answer 1

The correct option is B double

Since we are doubling the frequency, the energy of the photo-electron increases. To understand why the kinetic energy increases by more than two times, take a look at the photo-electric equation:

Initially,

$K_1=hf-\varphi$

When we double the frequency from f to 2f,

$K_2=h\left(2f\right)-\varphi$

or, $K_2=2(hf-\varphi )+\varphi$

So, a double in frequency causes a more than two times increase in Kinetic Energy.