The energy of a photon of frequency ν is hν and Einstein's photoelectric equation appears as K = hν − φ, so this Class 12 sheet opens by pairing quantum energy with the work function. The key also records h/p for de Broglie wavelength and a particle-nature answer.
Key Takeaways
Photon energy is E = hν (Q1).
Einstein's photoelectric equation is K = hν − φ (Q2).
The key records h/p as a de Broglie wavelength answer.
Section A: Multiple Choice Questions (1 Mark Each)
Choose the correct option for each question.
1.The energy of a photon of frequency ν is:
(a) hc(b) hν(c) h/ν(d) hcν
2.Einstein's photoelectric equation is:
(a) K = hν(b) K = φ − hν(c) K = hν − φ(d) K = hνφ
3.The de Broglie wavelength associated with a particle of momentum p is:
(a) h/p(b) hp(c) p/h(d) h/p²
4.The stopping potential for a given photosensitive surface depends on the:
(a) intensity of incident light(b) frequency of incident light(c) both equally(d) neither
5.The photoelectric effect demonstrates that light has:
(a) only wave nature(b) no nature(c) particle nature(d) wave nature only in vacuum
6.The work function of a metal is the:
(a) minimum energy needed to eject an electron(b) maximum energy of a photon(c) energy of a photon of red light(d) kinetic energy of the free electrons in the metal
Section B: Short Answer Type Questions (2 Marks Each)
Show all steps clearly.
7.State Einstein's photoelectric equation and define each term in it.
8.What is the work function of a metal? Give its unit.
9.Define stopping potential and threshold frequency.
10.State the laws of photoelectric emission.
11.State de Broglie's hypothesis and write the expression for the de Broglie wavelength of a particle.
12.What is meant by the dual nature of radiation and matter?
13.Why does the kinetic energy of the emitted photoelectrons not depend on the intensity of the incident light?
14.What happens to the photoelectric current and the kinetic energy of photoelectrons when the frequency of the incident light is increased above the threshold frequency?
Section C: Numericals & Word Problems (3 Marks Each)
Apply the concepts to solve the problems. Show all working.
15.A photon has a frequency of 5 × 10¹⁴ Hz. Using E = hν with h = 6.63 × 10⁻³⁴ J·s, find its energy in joules and in eV. Take 1 eV = 1.6 × 10⁻¹⁹ J.
16.The work function of a metal is 2 eV. Light of frequency 10¹⁵ Hz falls on it. Using K = hν − φ with h = 6.63 × 10⁻³⁴ J·s and 1 eV = 1.6 × 10⁻¹⁹ J, find the maximum kinetic energy of the emitted electrons in eV.
17.The threshold frequency of a metal is 4 × 10¹⁴ Hz. Light of frequency 6 × 10¹⁴ Hz is incident on it. Using K = h(ν − ν₀) with h = 6.63 × 10⁻³⁴ J·s, find the maximum kinetic energy of the emitted electrons.
18.Using λ = h/mv with h = 6.63 × 10⁻³⁴ J·s and m = 9.1 × 10⁻³¹ kg, find the de Broglie wavelength of an electron moving with a speed of 10⁶ m/s.
19.Light of wavelength 400 nm is incident on a metal of work function 1.9 eV. Using E = hc/λ with h = 6.63 × 10⁻³⁴ J·s, c = 3 × 10⁸ m/s and 1 eV = 1.6 × 10⁻¹⁹ J, find the energy of each photon and the maximum kinetic energy of the emitted electrons.
20.Light of frequency 8 × 10¹⁴ Hz falls on a metal whose work function is 2 eV. Using eV₀ = hν − φ with h = 6.63 × 10⁻³⁴ J·s and 1 eV = 1.6 × 10⁻¹⁹ J, find the stopping potential for the emitted electrons.
Answer Key
1. b) hν
2. c) K = hν − φ
3. a) h/p
4. b) frequency of incident light
5. c) particle nature
6. a) minimum energy needed to eject an electron
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End of Worksheet
People Also Ask
What is the energy of a photon of frequency ν?
hν, option (b) in this worksheet (Q1).
What is Einstein's photoelectric equation?
K = hν − φ, option (c) in this worksheet (Q2).
What is the de Broglie wavelength formula?
h/p, from the answer key on this page.
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