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← IIT-JEE 2010 · Paper 1
PhysicsInteger+3Question 76 of 84

IIT-JEE 2010 · Paper 1, Physics question 76

An α\alpha-particle and a proton are accelerated from rest by a potential difference of 100V. After this, their de Broglie wavelengths are λα\lambda_\alpha and λp\lambda_p respectively. The ratio λpλα\dfrac{\lambda_p}{\lambda_\alpha}, to the nearest integer, is

Answer and worked solution

Official answer: 3

Wavelength after acceleration. λ=h2mqV\lambda=\dfrac h{\sqrt{2mqV}}.

Ratio. mα=4mpm_\alpha=4m_p and qα=2qpq_\alpha=2q_p:
λpλα=mαqαmpqp=8≈2.83,\frac{\lambda_p}{\lambda_\alpha}=\sqrt{\frac{m_\alpha q_\alpha}{m_pq_p}}=\sqrt8\approx2.83,
which is 3 to the nearest integer.

Answer: 3