The Small Ozone Layer on Top of the Stratosphere is Crucial for Human Survival. Why? - Physics

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The small ozone layer on top of the stratosphere is crucial for human survival. Why?



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.

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Chapter 8: Electromagnetic Waves - Exercise [Page 287]


NCERT Physics Class 12
Chapter 8 Electromagnetic Waves
Exercise | Q 8.15 (d) | Page 287
NCERT Physics Class 12
Chapter 8 Electromagnetic Waves
Exercise | Q 15.4 | Page 287

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What role dose infra-red radiation play in maintain the Earth’s warmth

Identify the part of the electromagnetic spectrum which is suitable for radar system used in aircraft navigation.

Give a reason for the following:

Long-distance radio broadcasts use short-wave bands. Why?

Give a reason for the following:

It is necessary to use satellites for long-distance TV transmission. Why?

State Moseley's law

Write the approximate wavelengths for (i) blue and (ii) red light.

Which radiation is used for satellite communication?

What is the range of the wavelength of the following electromagnetic waves?

(a) Ultraviolet

What is the range of the wavelength of the following electromagnetic waves?

(a) Micro waves .

State the approximate range of wavelength associated with infrared rays.

Name the rays or waves produced by the changes in the nucleus of an atom .

Name three properties of ultraviolet radiations which are similar to visible light.

When a Coolidge tube is operated for some time it becomes hot. Where does the heat come from?

In a Coolidge tube, electrons strike the target and stop inside it. Does the target get more and more negatively charged as time passes?

Can X-rays be polarised?

Characteristic X-rays may be used to identify the element from which they are being emitted. Can continuous X-rays be used for this purpose?

Why is exposure to X-rays injurious to health but not exposure to visible light, when both are electromagnetic waves?

An X-ray beam can be deflected

Moseley's Law for characteristic X-ray is √v = a(Z − b). Here,

50% of the X-ray coming from a Coolidge tube is able to pass through a 0.1 mm thick aluminium foil. The potential difference between the target and the filament is increased. The thickness of the aluminium foil that will allow 50% of the X-ray to pass through will be

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 Kβ X-ray of argon has a wavelength of 0.36 nm. The minimum energy needed to ionize an argon atom is 16 eV. Find the energy needed to knock out an electron from the K shell of an argon atom.

The electric current in an X-ray tube (from the target to the filament) operating at 40 kV is 10 mA. Assume that on an average, 1% of the total kinetic energy of the electron hitting hte target are converted into X-rays.
(a) What is the total power emitted as X-rays and (b) how much heat is produced in the target every second?

The wavelength of Kα X-ray of tungsten is 21.3 pm. It takes 11.3 keV to knock out an electron from the L shell of a tungsten atom. What should be the minimum accelerating voltage across an X-ray tube having tungsten target which allows production of Kα X-ray?

(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)

A certain element emits Kα X-ray of energy 3.69 keV. Use the data from the previous problem to identify the element.

(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)

The electron beam in a colour TV is accelerated through 32 kV and then strikes the screen. What is the wavelength of the most energetic X-ray photon?

(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)

Write the range of the wavelength of the following electromagnetic radiations:
(a) Infrared rays
(b) Ultraviolet rays
(c) γ -rays

Write one use of each of the above.

Name the scientist who discovered Microwaves 

State the name and the range of wavelength of the invisible electromagnetic waves beyond the red end of the visible spectrum.

Name three radiations and their wavelength range which are invisible and beyond the violet end of the visible spectrum.

State one harmful effect each of the ultraviolet and infrared radiation.

To which regions of the electromagnetic spectrum do the following wavelengths belong: 
(a) 250 nm 
(b) 1500 nm 

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.

Name the part of the electromagnetic spectrum which is: 
Produced by bombarding a metal target with high electrons.

Calculate the shortest wavelength of electromagnetic radiation present in Balmer series of hydrogen spectrum.

Name the radiation of the electromagnetic spectrum which is used for the following:

Radar and Give the frequency range.

Name two sources of infrared radiation.

Give one use of electromagnetic radiations in Infrared radiation.

Choose the correct option.

The EM wave emitted by the Sun and responsible for heating the Earth’s atmosphere due to greenhouse effect is

Choose the correct option.

Earth’s atmosphere is richest in

Choose the correct option.

How does the frequency of a beam of ultraviolet light change when it travels from air into glass?

Answer briefly.

Why are microwaves used in radar?

Answer briefly.

Can we produce a pure electric or magnetic wave in space? Why?

Answer briefly.

Does an ordinary electric lamp emit EM waves?

Answer briefly.

Why light waves travel in a vacuum whereas sound waves cannot?

Answer briefly.

What are the ultraviolet rays?

Answer briefly.

Give two uses of ultraviolet rays.

Answer briefly.

What are radio waves?

Answer briefly.

Give two uses of radio waves.

Answer briefly.

Name the most harmful radiation entering the Earth's atmosphere from outer space.

Answer briefly.

What is a carrier wave?

Answer briefly.

Why high-frequency carrier waves are used for the transmission of audio signals?

Solve the numerical problem.

Calculate the frequency in MHz of a radio wave of wavelength 250 m. Remember that the speed of all EM waves in a vacuum is 3.0 × 108 m/s.

Solve the numerical problem.

Calculate the wavelength in nm of an X-ray wave of frequency 2.0 × 1018 Hz.

Solve the numerical problem.

The speed of light is 3 × 108 m/s. Calculate the frequency of red light of a wavelength of 6.5 × 10−7 m.

Calculate the wavelength of a microwave of a frequency of 8.0 GHz.

Which of the following is a tool used for separating the different color wavelengths from each other?

A car is moving towards a high cliff. The car driver sounds a horn of frequency f. The reflected sound heard by the driver has a frequency 2f. If v be the velocity of sound, then the velocity of the car, in the same velocity units, will be:

Microwaves are electromagnetic waves with frequency in the range of.

The frequency of x-rays, y-rays and ultraviolet rays are respectively a, b and c. Then:-

Following QN ∴ 14, the radiation force on the roof will be

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 frequency of e. m waves which is best suited .to observed of radius 3 × 10–4 his of the order of

Ozone layer above the earth's atmosphere will

Find the photon energy in units of ev for electromagnetic wave if waves length 40 m. Given h = 6.63 × 10–34 J.

A radio can tune to any station in the 7.5 mHz to 12 MHz band. What is corresponding wave length band.

SONAR emits which of the following waves?

If λv, λx and λm Am represents the wavelength of visible light, x-ray and microwaves respectively, then ______.

All components of the electromagnetic spectrum in a vacuum have the same ______

One requires 11eV of energy to dissociate a carbon monoxide molecule into carbon and oxygen atoms. The minimum frequency of the appropriate electromagnetic radiation to achieve the dissociation lies in ______.

The electric field intensity produced by the radiations coming from 100 W bulb at a 3 m distance is E. The electric field intensity produced by the radiations coming from 50 W bulb at the same distance is ______.

Electromagnetic waves with wavelength

  1. λ1 is used in satellite communication.
  2. λ2 is used to kill germs in water purifies.
  3. λ3 is used to detect leakage of oil in underground pipelines.
  4. λ4 is used to improve visibility in runways during fog and mist conditions.
  1. Identify and name the part of electromagnetic spectrum to which these radiations belong.
  2. Arrange these wavelengths in ascending order of their magnitude.
  3. Write one more application of each.

The half-value thickness of an absorber is defined as the thickness that will reduce exponentially the intensity of a beam of particles by a factor of 2. The half-value thickness in (µm) for lead assuming X-ray beam of wavelength 20 pm, µ = 50 cm-1 for X-rays in lead at wavelength λ = 20 pm, is ______ µm.

In uranium (Z = 92) the K absorption edge is 0.107 Å and the Kα line is 0.126 Å, and the wavelength of the L absorption edge is ______.

Given below in the left column are different modes of communication using the kinds of waves given in the right column. 

A.  Optical Fibre
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.

Which is the correct ascending order of wavelengths?

Photons of an electromagnetic radiation has an energy 11 keV each. To which region of electromagnetic spectrum does it belong? 


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