Question

the speed of light is 3×10^8 ms-¹ how many minutes does it takes the light of the sun to reach us on earth which is 1.5×10⁸ km away​

Answer 1

Need to FinD :-

• The time taken by light to come from sun to earth.

$\red{\frak{Given}}\begin{cases}\sf The\ speed \ of \ light \ is \ 3 * 10^8 \ m/s. \\\\\sf The \ earth \ is \ 1.5 \times 10^8 \ km\ away \ from \ earth . \end{cases}$

Given that the earth is 1.5 × 10⁸ km away from the sun . And we need to find the time taken by the light to come from sun to earth . We know that for uniform motion ,

$\sf\longrightarrow Distance = Speed \times Time$

So that ,

• Here Distance = 1.5 × 10⁸km
• The speed is 3 × 10⁸ m/s .
• Time = ?

On substituting the respective values ,

$\sf\longrightarrow 1.5 \times 10^8 km = 3\times 10^8 m/s * t \\\\\\\sf\longrightarrow 1.5 \times 10^{8+3} m = 3\times 10^8 m/s * t \\\\\\\sf\longrightarrow 1.5 \times 10^{11} m = 3\times 10^8 m/s * t \\\\\\\sf\longrightarrow t =\dfrac{ 1.5 \times 10^{11} m }{3 \times 10^8 m/s } \\\\\\\sf\longrightarrow t = \dfrac{ 10^3}{ 2} s \\\\\\\sf\longrightarrow t = 500s \\\\\\\sf\longrightarrow \underline{\underline{\red{ Time_{(\tiny From\ sun \ to \ earth )}= 8min \ 20s \approx 8.33 \ minutes }}}$