Ncert Exercises & Solutions

Electromagnetic waves with a wavelength:

(i) $λ_{1}$ is used in satellite communication.
(ii) $λ_{2}$ is used to kill germs in water purifiers.
(iii) $λ_{3}$ is used to detect leakage of oil in underground pipelines.
(iv) $λ_{4}$ is used to improve visibility in runways during fog and mist conditions.

(a) Identify and name the part of the electromagnetic spectrum to which these radiations belong.

(b) Arrange these wavelengths in ascending order of their magnitude.

Hint: The radiations can be classified as per their applications.

Step 1: Find the type of waves.

(i) Microwaves are used in satellite communications.
So,

λ_{1}

is the wavelength of the microwaves.

(ii) Ultraviolet rays are used to kill germs in water purifiers. So,

λ_{2}

is the wavelength of UV rays.

(iii) X-rays are used to detect leakage of oil in underground pipelines. So,

λ_{3}

is the wavelength of X-rays.

(iv) Infrared is used to improve visibility on runways during fog and mist conditions. So, it is the wavelength of infrared waves.

Step 2: Arrange them according to their wavelengths.

(b) Wavelength of X-rays < wavelength of UV < wavelength of infrared < wavelength of the microwave.

\Rightarrow

λ_{3}

λ_{2}

λ_{4}

λ_{1}

(c) (i) Microwaves are used in radar.
(ii) UV is used in LASIK eye surgery.
(iii) X-ray is used to detect a fracture in bones.
(iv) Infrared is used in optical communication.

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