Question

Solar energy is incident normally on the earth's surface at the rate of about 1.4 kW $m^{-2}$ . The distance between the earth and the sun is $1.5\times {10}^{11}$ m. Energy (E) and mass (M) are related by Einstein equation $E=m{c}^2$ where c $(3\times {10}^{8}m{s}^{-1})$ is the speed of light in free space. The decrease in the mass of the sun is

• A. ${10}^{9}kg{s}^{-1}$
• B. ${10}^{30}kg{s}^{-1}$
• C. ${10}^{26}kg{s}^{-1}$
• D. ${10}^{11}kg{s}^{-1}$

Answer 1

Answer: (A)

${10}^{9}kg{s}^{-1}$

Total energy E=$1.4\times {10}^3\times 4\pi r^2$

$r$=$1.5\times {10}^{11}$

$m=\frac{E}{c^2}={10}^{9}kg/s$