Question

For 7.7 Mev alpha particles scattering from aluminium (Z = 13), the distance of closest approach in a bead on collision is ______.

Useful data

`1/(4 pi ∈_0) = 8.99 xx 10^9` newton m²C^-2; c = 1.60 × 10^-19 C; leV = 1.60 × 10^-19j.

Options

• 2.4 × 10^-15 m

• 4.9 × 10^-15 m

• 2.4 × 10^-14 m

• 4.9 × 10^-14 m

Answer 1

For 7.7 Mev alpha particles scattering from aluminium (Z = 13), the distance of closest approach in a bead on collision is 4.9 × 10^-15 m.

Explanation:

K.E. = `("kq"_1"q"_2)/"r"_"closest"`

= `7.7 xx 10^6 xx 1.6 xx 10^-19`

`= (9 xx 10^9 xx 2 xx 1.6 xx 10^-19 xx 13 xx 1.6 xx 10^-19)/"r"_"closest"`

`"r"_"closest" = 4.86 xx 10^-15 "m" = 4.9 xx 10^-15`m