Modern Physics Practice Questions
HSC/SSC (Bangladesh) · HSC Physics · 143 free MCQs with instant results and detailed explanations.
143
Total
50
Easy
71
Medium
22
Hard
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Sample Questions from Modern Physics
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Q1
Easy
What is the primary function of a photomultiplier tube?
A.
To detect light and amplify it
B.
To measure air pressure
C.
To generate sound waves
D.
To produce electrical energy
Show Answer & Explanation
Correct Answer: A
A photomultiplier tube is designed specifically to detect light and amplify its intensity, making it very sensitive to low levels of light.
Q2
Easy
If a radioactive substance has a half-life of 10 years, how much of a 100g sample will remain after 30 years?
A.
12.5 g
B.
25 g
C.
50 g
D.
75 g
Show Answer & Explanation
Correct Answer: A
After 30 years (3 half-lives), the sample reduces as follows: 100g -> 50g -> 25g -> 12.5g, hence 12.5g remains.
Q3
Easy
What is the significance of the photoelectric effect in modern physics?
A.
It demonstrates the wave nature of light.
B.
It shows that light can be treated as particles.
C.
It explains why sound travels faster in air.
D.
It is used to measure temperature changes.
Show Answer & Explanation
Correct Answer: B
The photoelectric effect provides evidence that light can behave like particles, known as photons, which are crucial in understanding quantum mechanics.
Q4
Medium
In a photoelectric effect experiment, if the intensity of light is doubled while the frequency remains unchanged, what happens to the number of emitted electrons?
A.
Increases
B.
Decreases
C.
Remains unchanged
D.
Becomes zero
Show Answer & Explanation
Correct Answer: A
Doubling the intensity of light while keeping the frequency constant increases the number of photons striking the surface. Since each photon can potentially eject one electron, the number of emitted electrons will increase.
Q5
Medium
Which of the following statements about nuclear fusion is true?
A.
It occurs at low temperatures and pressures.
B.
It releases energy by combining light nuclei.
C.
It produces long-lived radioactive waste.
D.
It is the process used in atomic bombs.
Show Answer & Explanation
Correct Answer: B
Nuclear fusion involves the merging of light nuclei, such as hydrogen isotopes, to form heavier nuclei, releasing energy in the process. This is different from fission, which splits heavy nuclei.
Q6
Medium
In quantum mechanics, what does the Heisenberg Uncertainty Principle state about the position and momentum of a particle?
A.
They can be measured simultaneously with arbitrary precision.
B.
The more accurately one is known, the less accurately the other can be known.
C.
They are always equal to each other.
D.
They are independent of each other.
Show Answer & Explanation
Correct Answer: B
The Heisenberg Uncertainty Principle states that there is a fundamental limit to the precision with which both position and momentum of a particle can be simultaneously known. This means that if you know one with high accuracy, the other becomes uncertain.
Q7
Medium
Which of the following describes the photoelectric effect?
A.
Electrons are emitted from a material when it absorbs light of any frequency.
B.
Electrons are emitted from a material only when the light frequency exceeds a certain threshold.
C.
Light is absorbed without affecting electron emission.
D.
Electrons are emitted regardless of the light intensity.
Show Answer & Explanation
Correct Answer: B
The photoelectric effect occurs when light of sufficiently high frequency strikes a material, resulting in the emission of electrons. If the frequency is below a certain threshold, no electrons will be emitted, regardless of the light's intensity.
Q8
Hard
A nucleus emits a beta particle and transforms into a new element. If the original nucleus has a mass of 238 u and the emitted beta particle has a mass of 0.00055 u, what is the mass of the new element formed in atomic mass units (u)?
A.
237.99945 u
B.
238.00055 u
C.
238.0000 u
D.
237.9990 u
Show Answer & Explanation
Correct Answer: A
When a beta particle is emitted, the mass of the nucleus decreases by the mass of the beta particle. Therefore, the new mass is calculated as 238 u - 0.00055 u = 237.99945 u.
Q9
Hard
An atomic nucleus emitting a gamma photon has an initial energy of 8 MeV. If the emitted photon carries away 2 MeV of energy, what is the remaining energy of the nucleus after the emission?
A.
6 MeV
B.
10 MeV
C.
4 MeV
D.
8 MeV
Show Answer & Explanation
Correct Answer: A
When the nucleus emits a gamma photon, it loses energy equal to the energy of the photon. The remaining energy in the nucleus after emitting a 2 MeV gamma photon from an initial 8 MeV is calculated as 8 MeV - 2 MeV = 6 MeV.
Q10
Hard
In a photoelectric experiment, light of frequency 8 ร 10ยนโด Hz strikes a metal surface with a work function of 3.2 eV. What is the maximum kinetic energy of the emitted electrons?
A.
0.97 eV
B.
1.58 eV
C.
2.08 eV
D.
3.2 eV
Show Answer & Explanation
Correct Answer: A
The maximum kinetic energy (KE) of the emitted electrons can be calculated using the photoelectric equation: KE = hf - ฯ. Here, h = 6.626 ร 10โปยณโด Jยทs and ฯ = 3.2 eV (which is 3.2 ร 1.6 ร 10โปยนโน J). Thus, KE = (6.626 ร 10โปยณโด)(8 ร 10ยนโด) - 3.2 ร 1.6 ร 10โปยนโน = 0.97 eV.
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Modern Physics โ HSC/SSC (Bangladesh) HSC Physics Practice Questions Online
This page contains 143 practice MCQs for the chapter Modern Physics in HSC/SSC (Bangladesh) HSC Physics. The questions are organized by difficulty โ 50 easy, 71 medium, 22 hard โ so you can choose the right level for your preparation.
Every question includes a detailed explanation to help you understand the concept, not just memorize answers. Take a timed quiz to simulate exam conditions, or practice at your own pace with no time limit.