SECTION A

Q1. Draw Energy Band diagrams of p-type and n-type semiconductors at temperature T > 0 K, depicting the donor and acceptor energy levels. Mention the significance of these levels. (2 marks)

Answer 1:

The Energy Band diagrams of p-type and n-type semiconductors at temperature T > 0 K are given below,

Significance of n-type and p-type semiconductor are,

The n-type semiconductors have small energy gap between donor level and conduction band so that they can be covered by thermally excited electrons easily.

The p- type semiconductors have small energy gap between acceptor level and valence  band so that they can be covered by thermally excited electrons easily. 

In p-type semiconductors, there is a small amount of energy that can cause an electron from its valence band to jump to an acceptor energy level. This creates “holes” in the electrons’ outer shells, making them the majority charge carriers in these particular types of semiconductors.

Electrons are the majority charge carriers in the conduction band. These electrons come from donor impurity atoms and require very little energy to move into the conduction band.

Learn more about Semiconductors

Q2. (a) Draw the graph showing the variation of the number (N) of scattered alpha particles with scattering angle (θ) in Geiger- Marsden experiment. Infer two conclusions from the graph. (2 marks)

(b) Plot suitable graphs to show the variation of photoelectric current with the collector plate potential for the incident radiation of

(i) Same intensity but different frequencies v₁,v₂,v₃  (v₁<v₂<v₃)

(ii) Same frequency but different intensities I₁,I₂,I₃ ( I₁<I₂<I₃)

Answer 2. (a)

The graph showing the variation of the number (N) of scattered alpha particles with scattering angle (θ) in the Geiger- Marsden experiment is given below,

Conclusion are as follows

• Most of the alpha particles pass through the gold foil without any deviation. 
• Few alpha particles gets deflected by 90° or more. 
• About 0.14% of the alpha particles gets reflected by larger angles.
• A very few alpha particles goes back retracing their path.

NOTE: Write any two conclusions

OR

Answer 2.(b)

i) Same Intensity and Different Frequency

The graph showing the variation of photoelectric current with the collector plate potential for the incident radiation of the same intensity but different frequencies v₁, v₂, v₃  (v₁<v₂<v₃) is given below,

ii) Same Frequency but Different Intensity

The graph showing the variation of photoelectric current with the collector plate potential for the incident radiation of the Same frequency but different intensities I₁, I₂, I₃ ( I₁<I₂<I₃) is given below,

Check Photoelectric Effect

Q3. Write the characteristics of a p-n junction that make it suitable for rectification. (2 marks)

Answer 3:

• Unidirectional conductivity: A diode is an electronic component with unidirectional conductivity, meaning that it allows the current to flow in only one direction. Because of this property, diodes are often used in rectification circuits to convert alternating current (AC) into direct current (DC). This further means that the diode conducts only when it is forward biased and does not conduct when it is reverse biased.
• Non-linear voltage-current relationship: A diode is an electrical component with two leads that has a low voltage drop when current passes through it in the forward direction. This makes diodes highly efficient components in circuits, as they suffer less power loss due to their low forward voltage drop.
• High reverse breakdown voltage: When a voltage is applied in the reverse direction to a p-n junction, it can reach a point where the junction breaks down and allows current to flow in the reverse direction.

CBSE Class 12 Previous Year’s Question Paper for Physics is a valuable resource for students By using the solution provided, students can also learn the appropriate method to answer the questions in the board examination.

Using the CBSE previous year’s paper for Physics, students can gain more confidence in attempting the board examination, as they get to know the areas where they are lacking in their preparation. Also, the mistakes made while attempting this question paper as a mock examination can be rectified to avoid the repetition of such errors in the board examinations.