Question

can someone please tell me the value ofspeed of light in vaccum

Answer 1

he speed of light in vacuum, commonly denoted c, is a universal physical constant important in many areas of physics. Its exact value is 299,792,458 metres per second (approximately 300,000 km/s (186,000 mi/s)[Note 3]). It is exact because by international agreement a metre is defined to be the length of the path travelled by light in vacuum during a time interval of 1/299792458 second.[Note 4][3] According to special relativity, c is the maximum speed at which all conventional matter and hence all known forms of information in the universe can travel. Though this speed is most commonly associated with light, it is in fact the speed at which all massless particles and changes of the associated fields travel in vacuum (including electromagnetic radiation and gravitational waves). 

Answer 2

Here is your answer

The actual value of speed of light in vacuum is 2.998×10^8 m/s
However for ease it is taken as
3×10^8m/s

HOPE IT IS USEFUL