Physics 11–12: Conceptual Mastery Challenge

Question 1

In Young's double-slit experiment, if white light is used instead of monochromatic light, what is observed at the central fringe?

Accepted Answer

A white fringe because all wavelengths have zero path difference there

Answer

A dark fringe due to destructive interference of all colors

Answer

A red fringe because red deviates the least

Answer

Separate colored fringes with no central maximum

Question 2

Why does a satellite in circular orbit appear weightless to astronauts inside it?

Accepted Answer

Because both the satellite and astronauts are in continuous free fall together

Answer

Because gravity is absent at orbital height

Answer

Because the satellite moves beyond Earth's gravitational field

Answer

Because the satellite's speed cancels the mass of the astronauts

Question 3

Which statement best explains why the sky appears blue during the day?

Accepted Answer

Air molecules scatter shorter wavelengths more strongly than longer wavelengths

Answer

Blue light is reflected by the oceans into the atmosphere

Answer

The Sun emits more blue light than any other visible color

Answer

Dust particles absorb red light completely before it reaches Earth

Question 4

When a metallic surface is exposed to light in the photoelectric effect, increasing the frequency of incident light above threshold mainly affects which quantity?

Accepted Answer

The maximum kinetic energy of emitted electrons

Answer

The number of protons in the metal

Answer

The work function of the metal

Answer

The direction of electron charge

Question 5

In a p-n junction diode under forward bias, the current rises sharply after a certain point mainly because

Accepted Answer

the barrier potential is reduced, allowing majority carriers to cross the junction more easily

Answer

the depletion region widens and blocks minority carriers

Answer

the junction becomes an insulator and stores charge

Answer

electrons stop diffusing and only holes remain mobile

Question 6

Why does the potential energy of a stretched spring increase even when the spring remains at rest after stretching?

Accepted Answer

Because energy is stored in the elastic deformation of the spring

Answer

Because motion continues invisibly inside the spring coils

Answer

Because gravity increases the mass of the spring

Answer

Because the spring gains electric charge while stretching

Question 7

In a transformer, why must the magnetic flux through the secondary coil change with time?

Accepted Answer

Only a changing magnetic flux can induce an emf in the secondary coil

Answer

A constant flux produces a larger induced current

Answer

The secondary coil works only if its resistance is zero

Answer

Magnetic flux must vanish completely for energy transfer to occur

Question 8

Which comparison between transverse and longitudinal waves is correct?

Accepted Answer

In transverse waves, particle vibration is perpendicular to wave propagation

Answer

Only longitudinal waves can transfer energy

Answer

Transverse waves cannot travel through solids

Answer

Longitudinal waves always travel faster than transverse waves in every medium

Question 9

What is the key reason Bohr's model successfully explained the line spectrum of hydrogen?

Accepted Answer

It introduced quantized electron orbits with fixed energy levels

Answer

It treated electrons as stationary charges outside the nucleus

Answer

It assumed energy is emitted continuously as electrons orbit

Answer

It showed that all atoms have identical nuclear charge

Question 10

Why is the terminal velocity of a falling object reached in air?

Accepted Answer

Because air resistance grows until it balances the net downward force

Answer

Because gravitational force becomes zero after some time

Answer

Because the object stops interacting with surrounding air molecules

Answer

Because the object's mass decreases steadily while falling

Physics 11–12: Conceptual Mastery Challenge

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