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प्रश्न
The small ozone layer on top of the stratosphere is crucial for human survival. Why?
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उत्तर
The small ozone layer on the top of the atmosphere is crucial for human survival because it absorbs harmful ultraviolet radiations present in sunlight and prevents it from reaching the Earth’s surface.
संबंधित प्रश्न
To which part of electromagnetic spectrum does a wave of frequency 3 × 1013 Hz belong?
A radio can tune in to any station in the 7.5 MHz to 12 MHz band. What is the corresponding wavelength band?
Given below are some famous numbers associated with electromagnetic radiations in different contexts in physics. State the part of the electromagnetic spectrum to which each belongs.
(a) 21 cm (wavelength emitted by atomic hydrogen in interstellar space).
(b) 1057 MHz (frequency of radiation arising from two close energy levels in hydrogen; known as Lamb shift).
(c) 2.7 K [temperature associated with the isotropic radiation filling all space-thought to be a relic of the ‘big-bang’ origin of the universe].
(d) 5890 Å - 5896 Å [double lines of sodium]
(e) 14.4 keV [energy of a particular transition in 57Fe nucleus associated with a famous high resolution spectroscopic method (Mössbauer spectroscopy)].
Give the range of wavelength of the electromagnetic waves visible to us.
What do you understand by the invisible spectrum?
Consider a photon of a continuous X-ray coming from a Coolidge tube. Its energy comes from
Moseley's Law for characteristic X-ray is √v = a(Z − b). Here,
For harder X-rays,
(a) the wavelength is higher
(b) the intensity is higher
(c) the frequency is higher
(d) the photon energy is higher.
The potential difference applied to an X-ray tube is increased. As a result, in the emitted radiation,
(a) the intensity increases
(b) the minimum wavelength increases
(c) the intensity remains unchanged
(d) the minimum wavelength decreases.
An X-ray tube operates at 40 kV. Suppose the electron converts 70% of its energy into a photon at each collision. Find the lowest there wavelengths emitted from the tube. Neglect the energy imparted to the atom with which the electron collides.
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
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.
Identify the part of the electromagnetic spectrum used in
(i) radar and
(ii) eye surgery. Write their frequency range.
Answer briefly.
Why light waves travel in a vacuum whereas sound waves cannot?
Answer briefly.
What are radio waves?
Which of the following is a tool used for separating the different color wavelengths from each other?
Given below in the left column are different modes of communication using the kinds of waves given in the right column.
| A. | Optical Fibre Communication |
P. | Ultrasound |
| B. | Radar | Q. | Infrared Light |
| C. | Sonar | R. | Microwaves |
| D. | Mobile Phones | S. | Radio Waves |
From the options given below, find the most appropriate match between entries in the left and the right column.
Identify the electromagnetic wave whose wavelength range is from about 10-3 m to about 10-1 m. Write one use of this.
Identify the electromagnetic radiation and write its wavelength range, which is used to kill germs in water purified. Name the two sources of these radiations.
What is the wavelength range of electromagnetic radiation used in radio broadcast?
