Advertisements
Advertisements
Question
Answer briefly.
Why light waves travel in a vacuum whereas sound waves cannot?
Advertisements
Solution
Light waves are electromagnetic waves that can travel in a vacuum where sound waves travel due to the vibration of particles of the medium. Without any particles present (like in a vacuum) no vibrations can be produced. Hence, the sound wave cannot travel through the vacuum.
APPEARS IN
RELATED QUESTIONS
If the earth did not have atmosphere, would its average surface temperature be higher or lower than what it is now? Explain.
To which part of electromagnetic spectrum does a wave of frequency 3 × 1013 Hz belong?
Use the formula λm T= 0.29 cm K to obtain the characteristic temperature ranges for different parts of the electromagnetic spectrum. What do the numbers that you obtain tell you?
Why are infra-red waves often called heat waves? Explain.
The wavelengths for the light of red and blue colours are roughly 7.8 × `10^7` m and 4.8 × `10^7` m respectively.
(a) Which colour has the greater speed in vacuum?
(b) Which colour has the greater speed in glass?
What is the range of the wavelength of the following electromagnetic waves?
(a)X-rays,
Give one use of gamma rays.
Name the rays or waves of highest frequency .
Name three properties of ultraviolet radiations which are similar to visible light.
An electromagnetic wave has a frequency of 500 MHz and a wavelength of 60 cm Calculate the velocity of the wave.
Name of physical quantity which remains same for microwaves of wavelength 1 mm and UV radiations of 1600 Å in vacuum.
If the operating potential in an X-ray tube is increased by 1%, by what percentage does the cutoff wavelength decrease?
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
A free atom of iron emits Kα X-rays of energy 6.4 keV. Calculate the recoil kinetic energy of the atom. Mass of an iron atom = 9.3 × 10−26 kg.
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
The stopping potential in a photoelectric experiment is linearly related to the inverse of the wavelength (1/λ) of the light falling on the cathode. The potential difference applied across an X-ray tube is linearly related to the inverse of the cutoff wavelength (1/λ) of the X-ray emitted. Show that the slopes of the lines in the two cases are equal and find its value.
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
Two waves A and B have wavelength 0.01 Å and 9000 Å respectively.
Name the two waves. compare the speeds of these waves when they travel in vacuum.
Arrange the following electromagnetic waves in increasing order of their frequencies (i.e. begin with the lowest frequency):
Visible light, y rays, X rays, microwaves, radio waves, infrared radiations, and ultraviolet radiation.
Name the part of the electromagnetic spectrum which is:
Suitable for radar systems used in aircraft navigation.
Define the term "Intensity" in the photon picture of electromagnetic radiation.
Name the radiation of the electromagnetic spectrum which is used for the following:
For taking photographs of the sky during the night and foggy conditions . Give the frequency range
Give one use of electromagnetic radiations in Infrared radiation.
Name the radiations used for the detection of fracture in bones.
State two uses of infrared radiations.
Answer briefly.
Give two uses of ultraviolet rays.
An e.m. wave exerts pressure on the surface on which it is incident. Justify.
The area to be covered for T.V telecast is doubled then the height of transmitting antenna (T.V tower) will have to be:-
The magnetic field of a beam emerging from a filter facing a floodlight is given by B0 = 12 × 10–8 sin (1.20 × 107z – 3.60 × 1015t) T. What is the average intensity of the beam?
Give any two uses of infrared waves.
Name the electromagnetic radiation whose frequency is 10 Hz.
