Write the expression for the maximum velocity of a photo electron, in terms of its cut off voltage V ∘ .

The maximum kinetic energy of a photo electron: K . E . m a x = 1 2 m v m a x 2 ............... 1 Here, m is mass of electron and v m a x is the maximum velocity of the ejected photo electron. Using Einstein's equation for photoelectric effect: K . E . m a x = e V ∘ ............... 2 Now, equating 1 and 2 , we get: 1 2 m v m a x 2 = e V ∘ ⇒ v m a x = 2 e V ∘ m Hence, the expression for maximum velocity of the photo electron is v m a x = 2 e V ∘ m .

A graph of stopping potential against incident frequency for two photo sensitive metals A and B is shown in the figure. Which of the two metals A and B has the higher threshold wavelength?

The x-intercept represents threshold frequency. Here, the threshold frequency of photo sensitive metals A is smaller than photo sensitive metals B . Hence, B has the higher threshold wavelength.

E M B I B E

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 11 - Dual Nature of Radiation and Matter>Goa Board-2019>Q 3

MEDIUM

12th Goa Board

IMPORTANT

Earn 100

In a photoelectric emission Stopping potential is constant. Which quantity of the incident radiation is kept constant ?

Important Questions on Dual Nature of Radiation and Matter

EASY

12th Goa Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 11 - Dual Nature of Radiation and Matter>Goa Board-2019>Q 4

In a photoelectric emission, Maximum kinetic energy of the emitted photoelectrons is constant. In each of the case, which quantity of the incident radiation is kept constant?