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 different in different directions

B) changes with the motion of the source

C) is the same for all inertial observers

D) depends on the speed of the observer

2 / 30

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

A) Different for different light sources

B) Dependent on the frequency of light only

C) Dependent on the observer’s velocity

D) Constant for all inertial reference frames

3 / 30

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

A) Proved Newton’s laws were completely wrong

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

C) Made all objects travel at the speed of light

D) Showed that light needs a material medium

4 / 30

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

A) Less than $\mathbf{c}$

B) Zero

C) Greater than $\mathbf{c}$

D) Equal to $\mathbf{c}$

5 / 30

Einstein’s assumption contradicted which classical concept?

A) Galilean velocity addition

B) Conservation of momentum

C) Conservation of energy

D) Newton’s third law

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) $\mathbf{0}$

B) $\mathbf{0.5\ c}$

C) $\mathbf{c}$

D) $\mathbf{1.5\ c}$

7 / 30

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

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

B) Light has no energy.

C) Mass has no relation with energy.

D) Time and space are absolute quantities.

8 / 30

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

A) Speed of any electromagnetic wave in a medium

B) Speed of a moving observer

C) Speed of sound

D) Speed of light in vacuum

9 / 30

The constancy of the speed of light explains why:

A) All observers measure identical time intervals.

B) Objects cannot move.

C) Different observers can measure different times and lengths.

D) Gravity does not exist.

10 / 30

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

A) Remain unchanged

B) Predict no motion

C) Not be required in its present form

D) Become a theory of gravity only

11 / 30

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

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

B) The nature of electromagnetic waves

C) The observer’s velocity

D) The properties of vacuum

12 / 30

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

A) Light travels slower than sound.

B) Light has no wave nature.

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

D) Light requires ether for propagation.

13 / 30

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

A) Measure the same value of light speed

B) Always measure different speeds of light

C) Observe light moving only with the source

D) Measure zero speed of light

14 / 30

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

A) Space and time are absolute and universal.

B) Electromagnetic waves exist.

C) Light travels in vacuum.

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) Elimination of energy conservation

D) Time dilation

16 / 30

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

A) Having no change

B) Running slower

C) Running faster

D) Stopping permanently

17 / 30

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

A) Valid only for light

B) Valid only on Earth

C) The same in all inertial frames

D) Different in every inertial frame

18 / 30

Why cannot ordinary velocity addition be applied to light?

A) Light has no energy.

B) Light speed remains constant for all inertial observers.

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) $\mathbf{c}$

B) $\mathbf{1.8\ c}$

C) $\mathbf{0.8\ c}$

D) $\mathbf{0.2\ c}$

20 / 30

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

A) Thermodynamics

B) Quantum mechanics only

C) Special theory of relativity

D) Classical mechanics

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

B) Observers cannot measure it.

C) Light has no interaction with matter.

D) Light has infinite mass.

23 / 30

Einstein’s assumption helped explain that measurements of length:

A) are always identical for everyone

B) cannot be performed

C) are independent of time

D) can depend on relative motion

24 / 30

The constancy of light speed mainly affects our understanding of:

A) Chemical reactions only

B) Space and time

C) Mass only

D) Temperature only

25 / 30

Which statement correctly summarizes Einstein’s assumption?

A) Light speed depends on the source only.

B) Light speed changes with observer motion.

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

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) May not be simultaneous for another observer

B) Cannot occur in space

C) Must occur simultaneously for all observers

D) Always have equal energy

27 / 30

Einstein’s assumption was revolutionary because it showed that:

A) Motion has no effect on measurements.

B) Newtonian mechanics applies perfectly at all speeds.

C) Light has no wave properties.

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

28 / 30

The constant speed of light is approximately:

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

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

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

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

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) Dependent on source speed

D) Less than $\mathbf{c}$

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) Removed the need for experiments

C) Unified space and time into a relativistic framework

D) Established absolute time

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