Physics 11th Chap 13 : Topic 2 - Maryam Publications

Physics Chapter 13 : Topic 2

Constancy of the Speed of Light

1 / 30

Einstein’s assumption that the speed of light is constant means that the speed of light:

A) is the same for all inertial observers

B) depends on the speed of the observer

C) is different in different directions

D) changes with the motion of the source

2 / 30

According to Einstein’s second postulate, the speed of light in vacuum is:

A) Dependent on the observer’s velocity

B) Constant for all inertial reference frames

C) Dependent on the frequency of light only

D) Different for different light sources

3 / 30

The significance of Einstein’s assumption of constant speed of light was that it:

A) Made all objects travel at the speed of light

B) Showed that light needs a material medium

C) Required a modification of classical ideas about space and time

D) Proved Newton’s laws were completely wrong

4 / 30

In classical physics, if an observer moves toward a light source, the speed of light should appear:

A) Greater than $\mathbf{c}$

B) Zero

C) Equal to $\mathbf{c}$

D) Less than $\mathbf{c}$

5 / 30

Einstein’s assumption contradicted which classical concept?

A) Newton’s third law

B) Conservation of energy

C) Conservation of momentum

D) Galilean velocity addition

6 / 30

A spacecraft travels at half the speed of light toward a light beam. According to Einstein, the spacecraft observer measures the light speed as:

A) $\mathbf{1.5\ c}$

B) $\mathbf{0}$

C) $\mathbf{c}$

D) $\mathbf{0.5\ c}$

7 / 30

Einstein’s constant speed of light assumption led to the conclusion that:

A) Light has no energy.

B) Time and space are absolute quantities.

C) Time and space depend on the observer’s motion.

D) Mass has no relation with energy.

8 / 30

The symbol $\mathbf{(c)}$ in Einstein’s theory represents:

A) Speed of any electromagnetic wave in a medium

B) Speed of light in vacuum

C) Speed of a moving observer

D) Speed of sound

9 / 30

The constancy of the speed of light explains why:

A) Different observers can measure different times and lengths.

B) Objects cannot move.

C) All observers measure identical time intervals.

D) Gravity does not exist.

10 / 30

If the speed of light were not constant, Einstein’s theory of special relativity would:

A) Become a theory of gravity only

B) Predict no motion

C) Remain unchanged

D) Not be required in its present form

11 / 30

According to Einstein, the speed of light does not depend on:

A) The value of $\mathbf{c}$

B) The properties of vacuum

C) The observer’s velocity

D) The nature of electromagnetic waves

12 / 30

The famous Michelson-Morley experiment supported Einstein’s assumption by showing:

A) Light speed is independent of Earth’s motion.

B) Light travels slower than sound.

C) Light requires ether for propagation.

D) Light has no wave nature.

13 / 30

The constancy of light speed means that two observers moving relative to each other will:

A) Measure zero speed of light

B) Measure the same value of light speed

C) Observe light moving only with the source

D) Always measure different speeds of light

14 / 30

Einstein’s assumption required the rejection of the idea that:

A) Electromagnetic waves exist.

B) Light travels in vacuum.

C) Space and time are absolute and universal.

D) Energy can be conserved.

15 / 30

A major consequence of the constant speed of light is:

A) Decrease in speed of all objects

B) Increase in gravitational force only

C) Time dilation

D) Elimination of energy conservation

16 / 30

If a person travels close to the speed of light, an observer on Earth measures the traveler’s clock as:

A) Running faster

B) Having no change

C) Running slower

D) Stopping permanently

17 / 30

Einstein’s postulate implies that the laws of physics are:

A) Different in every inertial frame

B) Valid only on Earth

C) Valid only for light

D) The same in all inertial frames

18 / 30

Why cannot ordinary velocity addition be applied to light?

A) Light speed remains constant for all inertial observers.

B) Light has no energy.

C) Light does not obey conservation laws.

D) Light has no frequency.

19 / 30

If an observer moves at $\mathbf{0.8\ c}$ relative to a light source, the measured speed of light will be:

A) $\mathbf{0.8\ c}$

B) $\mathbf{0.2\ c}$

C) $\mathbf{1.8\ c}$

D) $\mathbf{c}$

20 / 30

Einstein’s assumption of constant light speed resulted in the development of:

A) Thermodynamics

B) Classical mechanics

C) Special theory of relativity

D) Quantum mechanics only

21 / 30

The constancy of speed of light shows that the universe has:

A) A preferred stationary frame

B) A universal rest position

C) No special inertial frame for measuring light speed

D) A fixed ether medium

22 / 30

The speed of light remains constant because:

A) Light has infinite mass.

B) It is a fundamental property of electromagnetic radiation in vacuum.

C) Light has no interaction with matter.

D) Observers cannot measure it.

23 / 30

Einstein’s assumption helped explain that measurements of length:

A) can depend on relative motion

B) are independent of time

C) are always identical for everyone

D) cannot be performed

24 / 30

The constancy of light speed mainly affects our understanding of:

A) Mass only

B) Chemical reactions only

C) Temperature only

D) Space and time

25 / 30

Which statement correctly summarizes Einstein’s assumption?

A) Light speed changes with observer motion.

B) Every inertial observer measures the same speed of light in vacuum.

C) Light speed depends on the source only.

D) Light cannot travel through vacuum.

26 / 30

A consequence of accepting constant speed of light is that two events occurring at the same time for one observer:

A) Always have equal energy

B) May not be simultaneous for another observer

C) Must occur simultaneously for all observers

D) Cannot occur in space

27 / 30

Einstein’s assumption was revolutionary because it showed that:

A) Light has no wave properties.

B) Newtonian mechanics applies perfectly at all speeds.

C) Space and time are linked with the speed of light.

D) Motion has no effect on measurements.

28 / 30

The constant speed of light is approximately:

A) $\mathbf{3 \times}\mathbf{10}^{\mathbf{4}}\mathbf{\ m/s}$

B) $\mathbf{3 \times}\mathbf{10}^{\mathbf{6}}\mathbf{\ m/s}$

C) $\mathbf{3 \times}\mathbf{10}^{\mathbf{8}}\mathbf{\ m/s}$

D) $\mathbf{3 \times}\mathbf{10}^{\mathbf{10}}\mathbf{\ m/s}$

29 / 30

If a light source moves toward an observer, the observer measures the light speed as:

A) Equal to $\mathbf{c}$

B) Greater than $\mathbf{c}$

C) Less than $\mathbf{c}$

D) Dependent on source speed

30 / 30

The most important significance of Einstein’s assumption of constant speed of light is that it:

A) Proved all objects travel at light speed

B) Unified space and time into a relativistic framework

C) Removed the need for experiments

D) Established absolute time

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