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CBSE Class 7 Answered

A particular star is at a distance of about 8.1*10000000000000km from the earth . Assuming that the light travels at 3*100000000 m/sec , find how long does light takes from that star to reach the earth .
Asked by Sanjay | 18 Apr, 2017, 08:07: PM
answered-by-expert Expert Answer
begin mathsize 14px style Distance space between space star space and space Earth equals 8.1 cross times 10 to the power of 13 space km equals 8.1 cross times 10 to the power of 13 cross times 10 cubed space straight m space space left parenthesis 1 space km space equals space 1000 space straight m right parenthesis SInce space light space travels space at space 3 cross times 10 to the power of 8 space straight m divided by straight s comma time space taken space by space light space to space reach space the space Earth equals fraction numerator 8.1 cross times 10 to the power of 13 cross times 10 cubed over denominator 3 cross times 10 to the power of 8 end fraction equals fraction numerator 8.1 cross times 10 to the power of 16 over denominator 3 cross times 10 to the power of 8 end fraction equals fraction numerator 8.1 over denominator 3 end fraction cross times 10 to the power of 8 equals 2.7 cross times 10 to the power of 8 space straight s end style
Answered by Rashmi Khot | 19 Apr, 2017, 02:22: PM

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