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Q1. Which colour of the visible spectrum has the greatest wavelength?

• 1) Yellow
• 2) Blue
• 3) Red
• 4) Violet

Solution

Red has the greatest wavelength in the visible spectrum.

Q2. The electric field for an em wave is: E = E₀sin[(12 x 10¹⁵ t – 4 x 10⁷ x)]. What is the speed of the em waves?

• 1) 4 x 10⁷ m / s
• 2) 3 x 10⁸ m / s
• 3) 48 x 10⁸ m / s
• 4) 12 x 10¹⁵ m / s

Solution

 c = w / k

Q3. Wavelength of visible Spectrum ranges from

• 1) 4 X 10^-7m to 7.8 X 10^-7m
• 2) 2 10^-7m to 8.8 X 10^-7m
• 3) 3 X 10^-7m to 7.8 X 10^-7m
• 4) 4.5 X 10^-7cm to 6.2 10^-7cm

Solution

Wavelength of visible Spectrum ranges from 4 X 10^-7m to 7.8 X 10^-7m.

Q4. Fractures are detected using

• 1) X - Rays
• 2) Microwaves
• 3) Infra red Rays
• 4) Visible Rays

Solution

Fractures are detected using X – Rays.

Q5. Which of the following has the dimensions of charge?

• 1)
• 2)
• 3)
• 4)

Solution

gives electric flux which has the dimensions of charge.

Q6. Electromagnetic Spectrum is

• 1) Orderly distribution of the electromagnetic radiations according to their wavelength or frequency.
• 2) Orderly distribution of the electromagnetic radiations according to their amplitude only.
• 3) Orderly distribution of the electromagnetic radiations according to their amplitude or frequency.
• 4) Orderly distribution of the electromagnetic radiations according to their wavelength or amplitude.

Solution

Electromagnetic Spectrum is orderly distribution of electromagnetic radiations according to their wavelength or frequency.

Q7. The electromagnetic waves produced when fast moving electrons are suddenly stopped by metal target of high atomic number are

• 1) Gamma rays
• 2) Visible rays
• 3) Infra - red rays
• 4) X - rays

Solution

X - Rays are produced when fast moving electrons are suddenly stopped by metal target of high atomic number.

Q8. Which region in the electromagnetic spectrum will have the highest speed?

• 1) Microwaves
• 2) All the regions have same speed
• 3) Radio
• 4) Visible

Solution

All the regions in the electromagnetic spectrum have the same speed. The speed depends on the material in which the wave is traveling.

Q9. The amplitude of the magnetic field is related to the amplitude of the electric field in an electromagnetic wave as

• 1)
• 2)
• 3)
• 4)

Solution

Q10. Electromagnetic waves constitute of

• 1) Electric and magnetic field varying in space and time tangentially and propagating through space such that the two fields are perpendicular to the direction of propagation.
• 2) Electric and magnetic field varying in space and time tangentially and propagating through space such that the two fields are perpendicular to the direction of propagation.
• 3) Electric and magnetic field varying in space and time sinusoidally and propagating through space such that the two fields are at 60 degrees to the direction of propagation.
• 4) Electric and magnetic field varying in space and time sinusoidally and propagating through space such that the two fields are perpendicular to the direction of propagation.

Solution

Electric and magnetic field varying in space and time sinusoidally and propagating through space such that the two fields are perpendicular to the direction of propagation .

Q11. Microwaves have wavelength in the range of

• 1) 400nm to 700 nm
• 2) 400 nm to 1 nm
• 3) 1mm to 1m
• 4) < 10 ^-12m

Solution

1mm to 1m

Q12. Infra red rays are used

• 1) In T.V. communication
• 2) Both in green house to keep plants warm and to treat muscular pain
• 3) In green house to keep plants warm
• 4) To treat muscular pain

Solution

Infra red rays are used a)     In green house to keep plants warm b)     To treat muscular pain

Q13. Which of the following, if any, can act as a source of electromagnetic waves. (i) A charge moving with a constant velocity (ii) A charge moving in a circular orbit. (iii) A charge at rest Give reason 

Solution

Only accelerated charge can radiate electromagnetic waves. As charge moving in a circular orbit is accelerated , so it can radiate electomagnetic waves.

Q14. Identify the part of the electromagnet spectrum which is        i. Suitable for radar system used in aircraft navigation.       ii. Adjacent to the low frequency of the electromagnetic spectrum      iii. Produced in nuclear reactions.      iv. Produced by bombarding a metal target by high speed electons.

Solution

(i) Microwaves (ii) Radiowaves (iii) Gamma rays (iv) X-rays

Q15. How is c related to ?

• 1)
• 2)
• 3)
• 4)

Solution

Q16. What is an electromagnetic wave?

Solution

The electric and magnetic fields varying in space and time sinusoidally and propagating through space such that the two fields are perpendicular to each other and perpendicular to the direction of propagation constitute an electromagnetic wave.

Q17. Which region in the electromagnetic spectrum has the highest frequency?

• 1) Visible
• 2) Radio
• 3) Gamma Radiation Region
• 4) Frequency is same for the complete spectrum

Solution

Gamma Radiation Region in the electromagnetic spectrum has the highest frequency.

Q18. State the properties of Electromagnetic Waves.

Solution

The properties of electromagnetic waves are: 1.    They are transverse in nature. 2.    They do not require any material medium for their propagation. 3.    Electromagnetic waves travel with a velocity 3 x 10⁸ m/s. 4.   They are produced by accelerated charges. 5.   These waves obey the principle of superposition.   

Q19. What is the relation between the wavelength and frequency?

Solution

Wavelength(λ) and frequency(f) are inversely related i.e. when wavelength increases frequency decreases or vice versa.

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