Define the ‘frequency’ and ‘time-period’ of a wave. What is the relation between the two?
Answer
The number of complete waves (or cycles) produced in one second is called frequency of the wave. The time required to produce one complete wave (or cycle) is called time-period of the wave. The time taken to complete one vibration is called time-period. Relation between time-period an frequency of a wave is: $\text{Frequency}=\frac{1}{\text{time period}}$
Can we hear (a) infrasonic waves (b) ultrasonic waves?
Answer
No, we cannot hear infrasonic waves and ultrasonic waves. That’s because the frequencies of both these waves fall beyond the human audible range of frequencies.
What will be the change in the wavelength of a sound wave in air if its frequency is doubled?
Answer
Velocity of sound = Frequency × wavelength Speed of sound in air is constant. Hence, frequency × wavelength = constant If frequency is doubled, wavelength is reduced to half.
State one observation from everyday life which shows that sound travels much more slow than light.
Answer
It is common observation that in the rainy season, the flash of lightning is seen first and the sound of thunder is heard a little later. That’s because, speed of light is very high as compared to speed of sound in air.