, Question 1
A charged particle moves in a uniform magnetic field with velocity
perpendicular to the field. If the particle's speed is doubled while the magnetic
field strength is halved, by what factor does the radius of its circular path
change?
A. It remains unchanged.
B. It doubles.
C. It quadruples.
D. It halves.
Correct Answer: C - It quadruples.
RATIONALE
The radius of the circular path is r = mv/(qB). Doubling v and halving
B gives a factor of (2)/(0.5) = 4, so the radius quadruples.
Question 2
A gas undergoes an isothermal expansion followed by an adiabatic
compression returning to its initial volume. Which statement about the net heat
transfer and work done over the entire cycle is correct?
A. Net heat transfer is zero, and net work done is zero.
B. Net heat transfer equals net work done, and both are non-zero.
C. Net heat transfer is positive, and net work done is negative.
D. Net heat transfer is negative, and net work done is positive.
Correct Answer: B - Net heat transfer equals net work done, and
both are non-zero.
RATIONALE
By the first law, for a closed cycle, U = 0, so Q_net = W_net. Since
the process is not a full Carnot cycle and involves irreversible paths,
net work and heat are generally non-zero.
Page 2
, Question 3
A double-slit experiment uses light of wavelength . If the entire apparatus is
immersed in a liquid with refractive index n > 1, what happens to the fringe
spacing?
A. It increases by a factor of n.
B. It decreases by a factor of n.
C. It remains unchanged because frequency is constant.
D. It decreases by a factor of n².
Correct Answer: B - It decreases by a factor of n.
RATIONALE
Fringe spacing is y = L/d. In a medium, the wavelength becomes /n, so
the spacing decreases by a factor of n.
Question 4
A parallel-plate capacitor is charged and then disconnected from the battery. A
dielectric slab is inserted, filling the gap. Which quantity remains constant?
A. Electric field between the plates
B. Potential difference across the plates
C. Charge on the plates
D. Energy stored in the capacitor
Correct Answer: C - Charge on the plates
RATIONALE
With the battery disconnected, charge cannot flow, so Q remains
constant. The capacitance increases, reducing V and E, and energy
decreases.
Question 5
A sound wave travels from air into water. Which property of the wave remains
unchanged across the boundary?
Page 3
, A. Wavelength
B. Speed
C. Frequency
D. Intensity
Correct Answer: C - Frequency
RATIONALE
Frequency is determined by the source and remains constant across
media. Speed and wavelength change according to the medium's
properties, and intensity may change due to reflection/transmission.
Question 6
In a photoelectric experiment, the stopping potential is measured for two
different wavelengths. If the wavelength is halved, how does the stopping
potential change?
A. It doubles.
B. It increases by a factor of 2 but offset by the work function.
C. It remains the same.
D. It decreases.
Correct Answer: B - It increases by a factor of 2 but offset by the
work function.
RATIONALE
Stopping potential V_s satisfies eV_s = hc/ - . Halving doubles the
photon energy term, but the work function remains, so V_s increases
but not simply by a factor of 2.
Question 7
A nucleus undergoes alpha decay. Which conservation law directly explains
the discrete energy spectrum of the emitted alpha particles?
A. Conservation of momentum
Page 4
A charged particle moves in a uniform magnetic field with velocity
perpendicular to the field. If the particle's speed is doubled while the magnetic
field strength is halved, by what factor does the radius of its circular path
change?
A. It remains unchanged.
B. It doubles.
C. It quadruples.
D. It halves.
Correct Answer: C - It quadruples.
RATIONALE
The radius of the circular path is r = mv/(qB). Doubling v and halving
B gives a factor of (2)/(0.5) = 4, so the radius quadruples.
Question 2
A gas undergoes an isothermal expansion followed by an adiabatic
compression returning to its initial volume. Which statement about the net heat
transfer and work done over the entire cycle is correct?
A. Net heat transfer is zero, and net work done is zero.
B. Net heat transfer equals net work done, and both are non-zero.
C. Net heat transfer is positive, and net work done is negative.
D. Net heat transfer is negative, and net work done is positive.
Correct Answer: B - Net heat transfer equals net work done, and
both are non-zero.
RATIONALE
By the first law, for a closed cycle, U = 0, so Q_net = W_net. Since
the process is not a full Carnot cycle and involves irreversible paths,
net work and heat are generally non-zero.
Page 2
, Question 3
A double-slit experiment uses light of wavelength . If the entire apparatus is
immersed in a liquid with refractive index n > 1, what happens to the fringe
spacing?
A. It increases by a factor of n.
B. It decreases by a factor of n.
C. It remains unchanged because frequency is constant.
D. It decreases by a factor of n².
Correct Answer: B - It decreases by a factor of n.
RATIONALE
Fringe spacing is y = L/d. In a medium, the wavelength becomes /n, so
the spacing decreases by a factor of n.
Question 4
A parallel-plate capacitor is charged and then disconnected from the battery. A
dielectric slab is inserted, filling the gap. Which quantity remains constant?
A. Electric field between the plates
B. Potential difference across the plates
C. Charge on the plates
D. Energy stored in the capacitor
Correct Answer: C - Charge on the plates
RATIONALE
With the battery disconnected, charge cannot flow, so Q remains
constant. The capacitance increases, reducing V and E, and energy
decreases.
Question 5
A sound wave travels from air into water. Which property of the wave remains
unchanged across the boundary?
Page 3
, A. Wavelength
B. Speed
C. Frequency
D. Intensity
Correct Answer: C - Frequency
RATIONALE
Frequency is determined by the source and remains constant across
media. Speed and wavelength change according to the medium's
properties, and intensity may change due to reflection/transmission.
Question 6
In a photoelectric experiment, the stopping potential is measured for two
different wavelengths. If the wavelength is halved, how does the stopping
potential change?
A. It doubles.
B. It increases by a factor of 2 but offset by the work function.
C. It remains the same.
D. It decreases.
Correct Answer: B - It increases by a factor of 2 but offset by the
work function.
RATIONALE
Stopping potential V_s satisfies eV_s = hc/ - . Halving doubles the
photon energy term, but the work function remains, so V_s increases
but not simply by a factor of 2.
Question 7
A nucleus undergoes alpha decay. Which conservation law directly explains
the discrete energy spectrum of the emitted alpha particles?
A. Conservation of momentum
Page 4
