5 % energy of a monochromatic light source is converted into light of wavelength 5600 A o . If the power of the source be 100 W , then how many photons of light will be emitted by it per second?

Given power of the source W = 100 W The wavelength og light = λ = 5600 × 10 - 10 m As power= energy per sec. = no . of photons × energy of each photon E = power no . ofphotons = 100 n As only 5 % is converted into the photons of wavelength 5600 ° A whose frequency is ν ' = c λ = 3 × 10 8 5600 × 10 - 7 = 5 . 357 × 10 14 H z As we require energy = hν ' = 5 n or n = 5 hv ' = 5 6 . 63 × 10 - 34 × 3 . 57 × 10 14 = 1 . 14 × 10 19 Hence the number of photons per sec= 1 . 14 × 10 19

5 % energy of a monochromatic light source is converted into light of wavelength 5600 A o . If the power of the source be 100 W , then how many photons of light will be emitted by it per second?

Given power of the source W = 100 W The wavelength og light = λ = 5600 × 10 - 10 m As power= energy per sec. = no . of photons × energy of each photon E = power no . ofphotons = 100 n As only 5 % is converted into the photons of wavelength 5600 ° A whose frequency is ν ' = c λ = 3 × 10 8 5600 × 10 - 7 = 5 . 357 × 10 14 H z As we require energy = hν ' = 5 n or n = 5 hv ' = 5 6 . 63 × 10 - 34 × 3 . 57 × 10 14 = 1 . 14 × 10 19 Hence the number of photons per sec= 1 . 14 × 10 19

E M B I B E

ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 8

HARD

12th ICSE

IMPORTANT

Earn 100

$5 %$ energy of a monochromatic light source is converted into light of wavelength $5600 \overset{o}{A}$ . If the power of the source be $100 W$ , then how many photons of light will be emitted by it per second?

Important Questions on Photoelectric Effect

HARD

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 9

Light of wavelength

5000 \overset{o}{A}

from a

2 W

bulb is falling on a surface. If the absorptive power of the surface be

60 %

, then how many photons are being absorbed by the surface per second? If

100

absorbed photons cause emission of

1

electron, then how much current will flow from the surface?

MEDIUM

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 11

Calculate the momentum of a photon of green light of

λ = 500 nm

in SI unit.(

h = 6.63 \times 10^{- 34} Js

)

MEDIUM

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 12

The energy of a photon is

42 e V

. Find out the momentum of the photon.

MEDIUM

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 13

The energy of a photon is

10 e V

. Calculate momentum of the photon.

MEDIUM

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 13

The energy of a photon is

10 eV

.Calculate wavelength of the photon.

MEDIUM

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 14

A photon ejects an electron of negligible kinetic energy from a metal surface. If the threshold frequency for the surface be

4.6 \times 10^{14} Hz

, Calculate the energy of the incident photon in electron-volt.

MEDIUM

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 10 - Photoelectric Effect>QUESTIONS>Q 15

A metal sheet has a negative charge of

11.2 nC (1 nC = 10^{- 9} C)

. How many photons of ultraviolet light are required to completely discharge the sheet by photoelectron ejection? What minimum amount of energy must be absorbed by the sheet to effect this discharge? The threshold frequency of the metal is