What is the number fo photons fo light with a wavelngth fo ` 400 p m` that provide ` 1 J ` of energy ?

Explanation

` E//"photon" = (hc)/ ( lambda) = (6.625 xx 10^(-34) xx 3 . 0 xx 10^8)/( 4000 xx 10^(-12))`
` = 4 . 97 xx 10^(-17)J`
`therefore` No . of photon in 1 J energy `= 1/( 4.97 xx 10 ^(-17))`
` 2. 01 xx 10 ^(16) ` photons .