[code1red1]

A diode laser emits a wavelength of 987 nm. All of its output energy is abosrbed in a detector that measures a total energy of 0.242 kJ. How many photons are being emitted by the laser?

[urmod4u]

Really, the fantasy of teachers has no limits.
A wavelength of 987 nm corresponds with a frequency of 3*10exp8/987*10exp(-9) Hz = 3/98.7 Hz. (3*10exp8 is the speed of the photon, aka the speed of light)
The energy of one photon is Planck's constant (6.626*10exp(-34)J.s) multiplied with the frequency, or 3*6.626/97.7*10exp34 J = 0.20345957*10exp(-34) J or scientifically 2.0345957*10exp(-35) J.
You need 242 J (=0.242 kJ) divided by that value to obtain the number of photons, which is 1.189425... *10exp37 photons.
Feel free to verify the calculations, I did not double check them.