A particular star is at a distance of about 8.1 × 10¹³ km from the Earth. Assuring that light travels at 3 × 10⁸ m per second, find how long does light takes from that star to reach the Earth.
Solution:
Given, a particular star is at a distance of about 8.1 × 10¹³ km from the Earth.
Assuring that light travels at 3 × 10⁸ m per second.
We have to find the time the light takes from that star to reach the Earth.
We know, speed = distance / time
Given, speed = 3 × 10⁸ m/s
Distance = 8.1 × 10¹³ km
We know, 1 km = 1000 m
= 8.1 × 10¹³ × 10³
Using the law of exponents,
am × an = am + n
= 8.1 × 1013 + 3
= 8.1 × 1016 m
Time = distance / speed
= 8.1 × 1016 / 3 × 108
= (8.1 / 3) × (1016/108)
= 2.7 × (1016/108)
Using the law of exponents,
am ÷ an = am - n
= 2.7 × 1016 - 8
= 2.7 × 10⁸ seconds
Therefore, the required time is 2.7 × 10⁸ seconds.
✦ Try This: A particular star is at a distance of about 2.7 × 10¹³ km from the Earth. Assuring that light travels at 3 × 10⁸ m per second, find how long does light takes from that star to reach the Earth.
☛ Also Check: NCERT Solutions for Class 8 Maths Chapter 12
NCERT Exemplar Class 8 Maths Chapter 8 Problem 174
A particular star is at a distance of about 8.1 × 10¹³ km from the Earth. Assuring that light travels at 3 × 10⁸ m per second, find how long does light takes from that star to reach the Earth.
Summary:
A particular star is at a distance of about 8.1 × 10¹³ km from the Earth. Assuring that light travels at 3 × 10⁸ m per second, the light takes 2.7 × 10⁸ seconds to reach the Earth from that star.
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