Dual Nature of Radiation And Matter

Previous Years' CBSE Board Questions

11.2 Electron Emission

MCQ.

The energy of a photon of wavelength <math>\lambda</math> is

1. <math>hc\lambda</math> (b) <math>hc/\lambda</math> (c) A/hc (d) λh/c

(2023)

(2021)

11.3 Photoelectric Effect

VSA (1 mark)

2 Define the term threshold frequency in photoelectric emission. (2020) R

OR

Define the term "threshold frequency", in the context of photoelectric emission. (Delhi 2019)

1. Define the term "Intensity" in photon picture of electromagnetic radiation. (Delhi 2019)

11.4 Experimental Study of Photoelectric Effect

Effect of Intensity of Light on Photocurrent

SAI (2 marks)

For the light of wavelength 400 nm incident on the

cathode of a photocell, the stopping potential is 6 V. If

the wavelength of incident light is increased to 600 nm,

calculate the new stopping potential.

<math>(Take h = 4.14 \times 10^{-15} eV s)</math>

1. (i) Monochromatic light of frequency 6.0 × 10¹⁴ Hz is produced by a laser. The power emitted is 2.0 × 10^-3 W. Estimate the number of photons emitted per second on an average by the source.
2. Draw a plot showing the variation of photoelectric current versus the intensity of incident radiation on a given photosensitive surface. (Delhi 2014) An

SAII (3 marks)

Light of wavelength 2000 Å is incident on a metal

surface of work function 4.2 eV in an experiment on

photoelectric effect.

Find the maximum kinetic energy (in eV) of

ejected photoelectrons.

1. If the intensity of light is doubled, find the change in stopping potential. (2020)
2. Plot a graph showing the variation of photoelectric

MCQ

1. Photons of energy 3.2 eV are incident on a photosensitive surface. If the stopping potential for the emitted electrons is 1.5 V, the work function for the surface is
2. 1.5 eV (b) 1.7 eV (c) 3.2 eV (d) 4.7 eV

(2023)

VSA. (1 mark)

5 If the frequency of the radiation incident on a photosensitive surface increases (u > un), how will the stopping potential change? (2021)

1. The three curves shown below, represent the variation of photocurrent and applied voltage for two different materials using two different intensities of a monochromatic light. Identify the two curves which are for the same material.

0 (2020)

1. In photoelectric effect, does the photoelectric current

(2019)

1. (a) Define the terms, (i) threshold frequency and
2. stopping potential in photoelectric effect.

1. Plot a graph of photocurrent versus anode potential for a radiation of frequency v and intensities <math>l_1</math> and <math>l_2</math> (<math>l_1 < l_2</math>). (Delhi 2019)

Photocurrent

Effect of Frequency of Incident Radiation on Stopping Potential

A 0 X

VSA (1 mark)

Val <math>M_1</math> <math>M_2</math>

The variation of the stopping potential (V₀) with the frequency

1. of the light incident on two different photosensitive surfaces <math>M_1</math> and <math>M_2</math> is shown in the figure.

Identify the surface which has greater value of the work function.

current with intensity of light. The work function for

the following metals is given.

Na: 2.75 eV and Mo: 4.175 eV.

Which of these will not give photoelectron emission

for a radiation of wavelength 3300 Å from a laser

beam? What happens if the source of laser beam is

brought closer? (Foreign 2016)

1. A beam of monochromatic radiation is incident on a photosensitive surface. Answer the following questions giving reasons.
2. Do the emitted photoelectrons have the same kinetic energy?
3. Does the kinetic energy of the emitted electrons depend on the intensity of incident radiation?
4. On what factors does the number of emitted photoelectrons depend? (Foreign 2015)

Effect of Potential on Photoelectric Current

VSA: (1 mark)

13. Draw graphs showing variation of photoelectric

current with applied voltage for two incident

radiations of equal frequency and different

intensities. Mark the graph for the radiation of

higher intensity. (2018)

SAL (2 marks)

depend on intensity of incident radiation? Give reasons. 14. Draw a graph showing variation of photocurrent with the anode potential of a photocell. (1/2, 2020)

1. The following graph shows the variation of photocurrent for a photosensitive metal:
2. Identify the variable X on the horizontal axis.
3. What does the point A on the horizontal axis represent?
4. Draw this graph for three different values of frequencies of incident radiation <math>v_1</math>, <math>v_2</math> and <math>v_3</math> <math>(v_1 > v_2 > v_3)</math> for same intensity.

0 Ð,

(d) Draw this graph for three different values

of intensities of incident radiation I1, I2 and I3

(2020)