A near UV photon of 300 nm is absorbed by a gas and then re-emitted as two photons. One photon is red with wavelength 760 nm. Hence, wavelength of the second photon is

• 1060 nm

• 496 nm

• 300 nm

• 215 nm

What transition in the hydrogen spectrum would have the same wavelength as the Balmer transition, n = 4 to n = 2 of He⁺ spectrum?

• n = 4 to n = 2

• n = 3 to n = 2

• n = 2 to n = 1

• n = 4 to n = 3

What is the degenercy of the level of H-atom that has energy $\left(-\frac{{\mathrm{R}}_{\mathrm{H}}}{9}\right)$ ?

• 16

• 9

• 4

• 1

What is the EAN of [Al(C₄O₄)₃]^3- ?

• 28

• 22

• 16

• 10

An isobar of ₂₀C⁴⁰ is

• ₁₈Ar⁴⁰

• ₂₀Ca³⁸

• ₂₀Ca⁴²

• ₁₈Ar³⁸

66.

In successive emission of $\mathrm{\alpha }$-and $\mathrm{\beta }$-particles, the number of $\mathrm{\alpha }$-and $\mathrm{\beta }$-particles should be emitted for the conversion of ₉₂U²³⁸ to ₈₂P²⁰⁶ are

• $7\mathrm{\alpha }, 5\mathrm{\beta }$

• $6\mathrm{\alpha }, 4\mathrm{\beta }$

• $4\mathrm{\alpha }, 3\mathrm{\beta }$

• $8\mathrm{\alpha }, 6\mathrm{\beta }$

An element _xA^y emits 5 α and 4β particles to give ₈₂B²⁰⁷. The number of protons and neutrons in A are respectively

• 88, 227

• 88, 139

• 82, 227

• 84, 139

Which of the following has the maximum penetrating power ?

• $\mathrm{\alpha }-$ particle

• $\mathrm{\gamma }-$particles

• Proton

• Positron

Which of the following travels with the speed of light?

• α-rays

• β-rays

• γ-rays

• X-rays

4 L- atom is equal to

• 40.50 cal

• 78.75 cal

• 95.23 cal

• 96 cal