KEAM 2018 Physics and Chemistry Paper

2 MeV neutron looses half of its
kinetic energy in each collision.
So, making geometric progression of each collisionIn this geometric progression,
a=2MeV
γ=‌

1

2

n th term,
an=arn−1
∴‌‌0.039=2×106(1/2)n−1
⇒‌‌1.95×10−8=(1/2)n−1
Taking log both sides,
Number of collision (n)=26.6≈26 collision