AP EAMCET Engineering 21 Apr 2019 Shift 2 Paper

The expression for the momentum of the photon,
p=‌

h

λ

mv=‌

h

λ

v=‌

h

mλ

From the formula for the Bohr's for H-atom,
‌

1

λ

=R(‌

1

n12

−‌

1

n22

)
Substitute the given values in theabove equation.
‌

1

λ

=(1.097×107)(‌

1

22

−‌

1

42

)
λ=4.86×10−7m
The recoil speed of photon is,
v=‌

6.62×10−34

1.6×10−27×4.86×10−7

v=0.8513m∕s
v=0.814m∕s