Energy and Momentum of Photon, Work Function, Threshold Wavelength Numerical Class-12 Nootan ISC Physics Solution Ch-23 Photoelectric Effect. Step by step solutions of Kumar and Mittal Physics of Nageen Prakashan as council latest prescribe guideline for upcoming exam. Visit official Website CISCE for detail information about ISC Board Class-12 Physics.
Energy and Momentum of Photon, Work Function, Threshold Wavelength Numerical Ch-23 Photoelectric Effect
| Board | ISC |
| Class | 12 |
| Subject | Physics |
| Book | Nootan |
| Chapter-23 | Photoelectric Effect |
| Topics | Numericals on Energy and Momentum of Photon, Work Function, Threshold Wavelength |
| Academic Session | 2025-2026 |
Class-12 Nootan ISC Physics Solutions Ch-23 Photoelectric Effect
Numericals on Energy and Momentum of Photon, Work Function, Threshold Wavelength
Que-1: Find the frequency of a photon of energy 75 eV.
Ans- Suppose that the frequency if υo
Que-2: The frequency of a beam of UV light is 1.0 × 10^15 Hz. What is the energy in one quantum of this light? Express it in eV. (ISC 2004)
Ans- Suppose that the energy is E then
Que-3: A certain spectral line has a wavelength of 400 nm. Calculate the frequency and energy of the photons associated with it.
Ans- Suppose that the frequency if υ and energy is E
Que-4: The energy of 600 nm photon is 3.30 x 10^-19 J. Find the energy of 400 nm photon.
Ans- Suppose that the energy is E
since E ∝ 1/λ
Que-5: Calculate the number of photons emitted per second from a monochromatic light source of 40 W, giving out light of wavelength 500 nm.
Ans- Suppose that the no. of photons is n then,
Que-6: Light of wavelength 500 nm falls on a sensitive surface. If the surface has received 10^-7 J energy, how many photons have fallen on the surface?
Ans-
Que-7: Find the number of photons of wavelength λ1 = 5.0 × 10^-5 cm whose total energy is equal to the energy of one photon of wavelength λ2 = 2.0 × 10^-12 cm. In which part of the electromagnetic spectrum do λ1 and λ2 fall?
Ans- Suppose that the no, of photons is n
ATQ E1 = E2
n.hc/λ1 = hc/λ2
λ1 and λ2 is visible and gamma cosmic rays
Que-8: 5% energy of a monochromatic light source is converted into light of wavelength 560 nm. If the power of the source be 100 W, then how many photons of light will be emitted by it per second?
Ans- According to Question
Que-9: Light of wavelength 500 nm 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?
Ans-
Que-10: The energy of a photon is 42 eV. Find out the momentum of the photon.
Ans-
Que-11: The energy of a photon is 10 eV. Calculate : (i) momentum of the photon, (ii) wavelength of the photon, (iii) rest mass and dynamic-mass of the photon.
Ans-(i) Momentum of photon
(ii) Wavelength of photon
(iii) Rest mass = 0
dynamic mass
Que-12: A photon ejects an electron of negligible kinetic energy from a metal surface. If the threshold frequency for the surface be 4.6 x 10^14 Hz, calculate the energy of the incident photon in electron-volt.
Ans- Suppose that the energy is E
Que-13: 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 4.5 x 10^15 Hz. discharge? The threshold frequency of the metal is
Ans- Suppose that the no of photon is n
Que-14: Assuming the visible region of the spectrum to be from 400 nm to 750 nm, calculate the maximum work function in electron-volt of a photo-cathode that can emit electrons with visible light of any wavelength.
Ans- Work function
Que-15: Calculate the threshold frequency of photon for photoelectric emission from a metal whose work function is 0.1 eV.
Ans- Threshold frequency
Que-16: The work function of sodium is 2.3 eV. Calculate the maximum wavelength in nm (nanometre) for the light that will cause photoelectrons to be emitted from sodium. (h = 6.63 x 10^-34 J s).
Ans- Maximum wavelength
Que-17: If the work function of a certain metal is 4.2 eV, will radiation of wavelength 330 nm incident on the surface emit electrons? Confirm it by calculation.
Ans- Threshold wavelength
Since, the given radiation has a wavelength longer than 294.6 nm, it cannot emit photoelectrons.
–: Energy and Momentum of Photon, Work Function, Threshold Wavelength Numerical :–
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