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Experimental Physics

NEET · Physics · Experimental Physics

A telescope observes two points on a distant planet. The linear...

A telescope observes two points on a distant planet. The linear separation between the points is π×106 m\pi \times 10^6 \text{ m}, and they subtend an angle of 6′6' (minutes of arc) at the telescope. The distance to the planet from the telescope is:

Options

  1. Aπ×107 m\pi \times 10^7 \text{ m}
  2. B1.8×109 m1.8 \times 10^9 \text{ m}
  3. C1.08×1011 m1.08 \times 10^{11} \text{ m}
  4. Dπ6×106 m\dfrac{\pi}{6} \times 10^6 \text{ m}

Correct answer

B. 1.8×109 m1.8 \times 10^9 \text{ m}

Step-by-step solution

The plane angle subtended by an arc of length ss at a distance DD is given by θ=sD\theta = \dfrac{s}{D}, provided θ\theta is measured in radians.

Given:

s=π×106 ms = \pi \times 10^6 \text{ m}

θ=6′\theta = 6'

First, convert the angle into radians:

6′=(660)∘=0.1∘6' = \left(\dfrac{6}{60}\right)^\circ = 0.1^\circ

0.1∘=0.1×π180 rad=π1800 rad0.1^\circ = 0.1 \times \dfrac{\pi}{180} \text{ rad} = \dfrac{\pi}{1800} \text{ rad}

Now, calculate the distance DD:

D=sθ=π×106π1800D = \dfrac{s}{\theta} = \dfrac{\pi \times 10^6}{\dfrac{\pi}{1800}}

D=1800×106 m=1.8×109 mD = 1800 \times 10^6 \text{ m} = 1.8 \times 10^9 \text{ m}

Answer: 1.8×109 m1.8 \times 10^9 \text{ m}
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