The laser beam of wavelength, λ=5×10−7 m strikes normally on a blackened plate and produces a force of 10−5 N.
Mass of plate is 10 g and its specific heat capacity is 400 J kg−1K−1 . The temperature rise of plate per second is x K. Then the value of x100 is (Answer upto two digits after decimal point)
Force = change in momentum of one photon × number of photons striking per second
E→ energy incident per second.
Now, msdθdt=c×10−5=3×103⇒dθdt=3×10310×10−3×400=750 K s−1