Dual Nature of Matter and Radiation

Question 1

Work function

Answer 1

Minimum energy required for emission of an electron

ϕ=hVo

Question 2

Threshold Frequency

Answer 2

minimum frequency of the incident radiation for emission of an electron from the surface of a metal

Question 3

Types of Electron Emission

Answer 3

1. Thermal emission
2. Field emission
3. Photoelectric emission

Question 4

Power

Answer 4

P=nhv/t

Question 5

Intensity

Answer 5

I=P/Area

Question 6

Variation of photoelectric current with intensity of incident light

Answer 6

Ip directly proportional to intensity

Question 7

Stopping potential depends on

Answer 7

frequency of incident radiation

Question 8

What is stopping potential

Answer 8

Negative potential applied to the collecting plate at which photoelectric current becomes zero

Question 9

What is the variation of stopping potential when the intensity of incident light is increased?

Answer 9

Stopping potential remains the same as, frequency of incident light remains the same

Question 10

Why is the photoelectric current non zero even when collecting plate potential is zero?

Answer 10

Some electrons have enough kinetic energy to reach the plate

Question 11

What is observed when frequency of incident light is increased and intensity is kept constant?

Answer 11

As the frequency of incident light is increase, energy of light is increased. As a result, maximum KE of electron is increased, so stopping potential is increased.
Saturated current remains constant as intensity of light remains constant.

Question 12

KEmax

Answer 12

eVo

Question 13

Einstein’s photoelectric equation

Answer 13

ϕ=hf−KE

Question 14

hc/e

Answer 14

1242 nm

Question 15

Why photoelectric effect is instantaneous?

Answer 15

Einstein explained photoelectric emission as elastic collision between the incident photon and the electron. At the same instant, when the photon is incident, the electron is emitted to conserve energy.

Question 16

Why the slope of graph between stopping potential and frequency of incident light is constant?

Answer 16

because slope=h/e which is a universal constant

Question 17

Debroglie’s hypothesis

Answer 17

Every moving matter has a wave associated with it known as debroglie wave or matter wave.

Question 18

Wavelength of matter wave

Answer 18

h/mv

Question 19

Why is wave character for macroscopic objects not observed

Answer 19

due to large momentum, wavelength is very small

Question 20

Expression for Debroglie wavelength of a charged particle accelerated by a potential difference

Answer 20

λ=h/√(2mqV)

Question 21

Debroglie wavelength of an electron accelerated by a potential difference

Answer 21

λ=12.27A/√V

where A is Angstrom unit