IIT-JEE 2008 Paper 1 Offline

MCQ (Single Correct Answer)

-1

In a mixture of H - He$$^+$$ gas (He$$^+$$ is singly ionized He atom), H atoms and He$$^+$$ ions are excited to their respective first excited states. Subsequently, H atoms transfer their total excitation energy to He$$^+$$ ions (by collisions). Assume that the Bohr model of atom is exactly valid.

The ratio of the kinetic energy of the $$n=2$$ electron for the H atom to that of He$$^+$$ ion is

$$\frac{1}{4}$$

$$\frac{1}{2}$$

IIT-JEE 2007 Paper 2 Offline

MCQ (Single Correct Answer)

-1

Electrons with de-Broglie wavelength $$\lambda$$ fall on the target in an X-ray tube. The cut-off wavelength of the emitted X-rays is

$$\lambda_{0}=\frac{2 m c \lambda^{2}}{h}$$

$$\lambda_{0}=\frac{2 h}{m c}$$

$$\lambda_{0}=\frac{2 m^{2} c^{2} \lambda^{3}}{h^{2}}$$

$$\lambda_{0}=\lambda$$

JEE Advanced Subjects