NEET UG Physics Practice Paper – Nuclei & Semiconductor (Set 15)

Attempt all 30 MCQs and check your score instantly.

1. Mass defect is:

difference in mass
total mass
energy
none

2. Binding energy is:

energy to break nucleus
energy to form atom
kinetic energy
none

3. Relation:

E=mc²
V=IR
F=ma
none

4. Half life:

N/2
N
2N
none

5. Decay law:

N=N₀e⁻λt
V=IR
F=ma
none

6. Unit of activity:

Becquerel
Joule
Watt
none

7. Alpha decay emits:

helium nucleus
electron
photon
none

8. Beta decay emits:

electron
proton
neutron
none

9. Gamma rays are:

EM waves
particles
neutrons
none

10. Nuclear force is:

strong
weak
electric
none

11. Semiconductor has:

moderate conductivity
high
zero
none

12. Intrinsic semiconductor:

pure
doped
conductor
none

13. Extrinsic semiconductor:

doped
pure
none
zero

14. n-type has:

electrons
holes
none
zero

15. p-type has:

holes
electrons
none
zero

16. Diode conducts in:

forward bias
reverse
none
zero

17. Reverse bias current:

small
large
zero
none

18. Zener diode used for:

voltage regulation
amplification
none
zero

19. Logic gate AND output:

1 when both 1
always 1
always 0
none

20. OR gate output:

1 if any 1
0 always
none
zero

21. NOT gate:

inverter
amplifier
none
zero

22. Semiconductor material:

silicon
copper
iron
none

23. Doping increases:

conductivity
resistance
none
zero

24. PN junction forms:

depletion layer
conductor
none
zero

25. Barrier potential exists in:

PN junction
conductor
none
zero

26. LED emits:

light
heat
sound
none

27. Transistor used for:

amplification
cooling
heating
none

28. Collector current is:

largest
smallest
equal
none

29. Semiconductor band gap:

small
large
zero
none

30. Conductivity increases with:

temperature
pressure
none
zero

Submit

NEET UG Physics Notes – Nuclei & Semiconductor (Set 15)

This combined chapter is part of Modern Physics + Electronics, and it is one of the highest scoring sections in NEET UG. Most questions are direct formula-based, conceptual, and easy to solve with proper revision.

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PART 1: NUCLEI

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1. Atomic Structure Basics

• Nucleus contains protons and neutrons
• Atomic number (Z) → number of protons
• Mass number (A) → protons + neutrons

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2. Mass Defect

Mass defect is the difference between:$$\text{Mass defect} = (\text{sum of nucleon masses}) – (\text{actual mass})$$Mass defect=(sum of nucleon masses)−(actual mass)

Reason:

• Some mass converts into energy

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3. Binding Energy

Energy required to separate nucleus into nucleons.$$E = \Delta m \, c^2$$E=Δmc2

Key Insight:

• Higher binding energy → more stable nucleus

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4. Binding Energy Curve

Important Observations:

• Maximum stability near iron (Fe)
• Light nuclei → fusion
• Heavy nuclei → fission

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5. Radioactive Decay Law

$$N = N_0 e^{-\lambda t}$$N=N0​e−λt

Where:

• $\lambda$λ = decay constant

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6. Half-Life (T₁/₂)

Time for number of nuclei to reduce to half.$$T_{1/2} = \frac{\ln 2}{\lambda}$$T1/2​=λln2​

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7. Activity

$$A = \lambda N$$A=λN

Unit:

• Becquerel (Bq)

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8. Types of Radioactive Decay

Alpha Decay (α):

• Emits helium nucleus
• Mass decreases by 4

Beta Decay (β):

• Emits electron
• Neutron → proton

Gamma Decay (γ):

• Emits EM radiation
• No change in mass or charge

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9. Nuclear Force

• Very strong and short-range
• Independent of charge

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10. Nuclear Energy

Fission:

• Heavy nucleus splits
• Example: Uranium

Fusion:

• Light nuclei combine
• Occurs in sun

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PART 2: SEMICONDUCTORS

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11. Conductors vs Semiconductors

Type	Conductivity
Conductor	High
Semiconductor	Moderate
Insulator	Low

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12. Intrinsic Semiconductor

• Pure semiconductor (Si, Ge)
• Equal electrons and holes

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13. Extrinsic Semiconductor

Doped semiconductor:

n-type:

• Majority carriers → electrons

p-type:

• Majority carriers → holes

---

14. PN Junction

Formed by joining p-type and n-type.

Depletion Region:

• Region with no charge carriers

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15. Barrier Potential

• Potential difference across junction
• Prevents charge flow

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16. Biasing of Diode

Forward Bias:

• Allows current flow

Reverse Bias:

• Blocks current (small leakage)

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17. Zener Diode

Use:

• Voltage regulation

---

18. LED (Light Emitting Diode)

• Emits light when forward biased
• Used in displays

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19. Transistor

Uses:

• Amplification
• Switching

Currents:

$$I_E = I_B + I_C$$IE​=IB​+IC​

---

20. Logic Gates

AND Gate:

• Output 1 only if both inputs 1

OR Gate:

• Output 1 if any input 1

NOT Gate:

• Inverts input

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21. Band Theory

Semiconductors:

• Small band gap

Effect of Temperature:

• Conductivity increases with temperature

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22. Important NEET Formulas

• $E = mc^2$E=mc2
• $N = N_0 e^{-\lambda t}$N=N0​e−λt
• $T_{1/2} = \ln2/\lambda$T1/2​=ln2/λ
• $A = \lambda N$A=λN

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23. Common Mistakes

❌ Confusing alpha, beta, gamma changes
❌ Forgetting half-life relation
❌ Mixing n-type and p-type carriers
❌ Ignoring diode biasing concept

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24. Quick Revision Tips

• Binding energy = stability indicator
• Decay is exponential
• Semiconductor → current via electrons & holes
• Diode works only in forward bias

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Conclusion

Nuclei + Semiconductor is a very high-scoring and easy section in NEET.

Focus on:

• Radioactive decay formulas
• Nuclear reactions
• PN junction concepts
• Logic gates

👉 With proper revision, you can secure full marks in this section easily.