Wave Optics Test

Result

Wave Optics Test - 38

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Weekly Quiz Competition

Question 1
4 / -1

A star moves away from earth at speed 0.8 c while emitting light of frequency 6 × 10¹⁴ Hz. What frequency will be observed on the earth? (in units of 10¹⁴ Hz) (c = speed of light)

A
0.24

B
1.2

C
30

D
3.3

Solution
Question 2
4 / -1

A light source approaches the observer with velocity 0.8 c. The doppler shift for the light of wavelength 5500 Å is

A
4400 Å

B
1833 Å

C
–3666 Å

D
7333 Å

Solution
Question 3
4 / -1

A heavenly body is receding from earth such that the fractional change in λ is 1, then its velocity is

A

B

C

D

Solution
Question 4
4 / -1

In the spectrum of light of a luminous heavenly body the wavelength of a spectral line is measured to be 4747 Å while actual wavelength of the line is 4700 Å. The relative velocity of the heavenly body with respect to earth will be (velocity of light is 3 × 10⁸ m/s)

A
3 × 10³ m/s moving towards the earth

B
3 × 10³ m/s moving away from the earth

C
3 × 10⁶ m/s moving towards the earth

D
3 × 10⁶ m/s moving away from the earth

Solution
Question 5
4 / -1

The wavelength of light observed on the earth, from a moving star is found to decrease by 0.05%. Relative to the earth the star is

A
Moving away with a velocity of 1.5 × 10⁵ m/s

B
Coming closer with a velocity of 1.5 × 10⁵ m/s

C
Moving away with a velocity of 1.5 × 10⁴ m/s

D
Coming closer with a velocity of 1.5 × 10⁴ m/s

Solution
Question 6
4 / -1

A star is going away from the earth. An observer on the earth will see the wavelength of light coming from the star

A
Decreased

B
Increased

C
Neither decreased nor increased

D
Decreased or increased depending upon the velocity of the star
Question 7
4 / -1

A star is moving towards the earth with a speed of 4.5 × 10⁶ m/s. If the true wavelength of a certain line in the spectrum received from the star is 5890 Å, its apparent wavelength will be about [c = 3 × 10⁸ m/s]

A
5890 Å

B
5978 Å

C
5802 Å

D
5896 Å

Solution
Question 8
4 / -1

Due to Doppler\'s effect, the shift in wavelength observed is 0.1 Å for a star producing wavelength 6000 Å. Velocity of recession of the star will be

A
2.5 km/s

B
10 km/s

C
5 km/s

D
20 km/s

Solution
Question 9
4 / -1

When the wavelength of light coming from a distant star is measured it is found shifted towards red. Then the conclusion is

A
The star is approaching the observer

B
The star recedes away from earth

C
There is gravitational effect on the light

D
The star remain stationary
Question 10
4 / -1

The velocity of a moving galaxy is 300 km s^–1 and the apparent change in wavelength of a spectral line emitted from the galaxy is observed as 0.5 nm. Then, the actual wavelength of the spectral line is

A
3000 Å

B
5000 Å

C
6000 Å

D
4500 Å

Solution