### NEET Solved Paper 2018 Question 14

##### Question: When the light of frequency $ 2v _0 $ (where $ v _0 $ is threshold frequency), is incident on a metal plate, the maximum velocity of electrons emitted is $ v _1 $ . When the frequency of the incident radiation is increased to $ 5v _0 $ , the maximum velocity of electrons emitted from the same plate is $ v _2 $ . The ratio of $ v _1 $ to $ v _2 $ is [NEET - 2018]

#### Options:

A) $ 4:1 $

B) $ 1:4 $

C) $ 1:2 $

D) $ 2:1 $

## Show Answer

#### Answer:

Correct Answer: C

#### Solution:

$ \text{E=}{W_0}\text{+}\frac{1}{2}m{v^{2}} $ $ \text{h(2}{v_0}\text{)=h}{v_0}\text{+}\frac{1}{2}mv_1^{2} $ $ h{v_0}\text{=}\frac{1}{2}mv_1^{2} $ ..(i)

$ \text{h(5}{v_0})=hv _0+\frac{1}{2}mv_2^{2} $ $ 4hv _0=\frac{1}{2}mv_2^{2} $ ..(ii)

Divide (i) by (ii) $ \frac{1}{4}=\frac{v_1^{2}}{v_2^{2}} $ $ \frac{v _1}{v _2}=\frac{1}{2} $