If nr and nb be respectively the number of photons emitted by a red bulb and a blue bulb of equal power in one second, then nr is
Let vr and vb be the freqencies of red and blue light respectively. We know that vb>vr.
Now, since the two sources emit with equal power, the energy emitted per second will be -
nr(hvr)=nb(hvb),
which would imply,
nrvr=nbvb.
Since vb>vr, we can directly conclude: nr>nb.