Physics
Assertion (A): The flash of lightning is seen before the sound of thunder is heard.
Reason (R): The speed of sound is greater than the speed of light.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true and R is not the correct explanation of A.
- assertion is false but reason is true.
- assertion is true but reason is false.
Answer
4. assertion is true but reason is false.
Explanation
Assertion (A) is true. The flash of lightning is seen before the sound of thunder is heard due to the difference in the speeds of light and sound. Light travels much faster than sound, so the flash of lightning is observed almost instantaneously, while the sound of thunder takes some time to travel to the observer.
Reason (R) is false. The speed of sound is not greater than the speed of light. Light travels faster than sound with a speed of 3 x 108 m/s whereas speed of sound is 330 m/s.
Related Questions
Assertion (A): If momentum of a body increases by 50%, its kinetic energy will increase by 125%.
Reason (R): Kinetic energy is proportional to the square of velocity.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true and R is not the correct explanation of A.
- assertion is false but reason is true.
- assertion is true but reason is false.
Assertion (A): The speed of sound in a gas increases with an increase in humidity.
Reason (R): Density of a gas decreases with increase in humidity.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true and R is not the correct explanation of A.
- assertion is false but reason is true.
- assertion is true but reason is false.
Assertion (A): When we start filling an empty pitcher with water, the pitch of the sound produced goes on decreasing.
Reason (R): The pitch of sound increases with increase in frequency.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true and R is not the correct explanation of A.
- assertion is false but reason is true.
- assertion is true but reason is false.
Assertion (A): A ray of light travelling from a rarer medium to a denser medium, slows down and bends away from the normal.
Reason (R): The speed of light is higher in a rarer medium than in a denser medium.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true and R is not the correct explanation of A.
- assertion is false but reason is true.
- assertion is true but reason is false.