Pramod (kendriya vidyalaya no 2, 16 yrs):
if mass can be converted into mass then energy can be converted into energy. Therefore light is a source of energy what is the mass of light
President APJ Abdul Kalam: It is indeed a good question. Even though light has no rest mass it does have an effective mass which has all the properties one expects from MASS -- in particular, it has weight in a gravitational field and exerts a gravitational attraction of its own on other masses. The classic Gedanken experiment on this topic is one in which the net mass of a closed box with mirrored sides increases if it is filled with light bouncing back and forth off the mirrors. Further, you can refer through a good search engine or from a good physics text book on light.
rajul nema (DELHI PUBLIC SCHOOL, BHILAI C.G., 9 yrs):
respected sir,technoly is growing, sir in your opinion after how much years we indian will be number one in the field of missile and when a common indian man will be able to visit moon, with regards, rajul nema
President APJ Abdul Kalam: India is one of the five important countries who have got satellite launch vehicle capability and spacecraft launching capability in India. We have number of remote sensing and communication satellites. Indian spacecraft will orbit the moon in 2007.
NITESH SONI (DAV School, Sec-8c Chandigarh, 13 yrs):
Mr. President, What's your first priority for the nation?
President APJ Abdul Kalam: Lifting the 260 million people from below the poverty line.
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