In a radioactive change $\mathrm{R} \stackrel{-\mathrm{\alpha }}{\to } \mathrm{X} \stackrel{-\mathrm{\beta }}{\to } \mathrm{Y} \stackrel{-\mathrm{\beta }}{\to } \mathrm{Z}$. R and Z.

• isotopes

• isobars

• isomers

• isotones

_nX^m emit one α and two β- particles. It is converted into

• _nX^{m - 4}

• _{n - 1}X^{m - 1}

• _nZ^{m - 4}

• None of these

Increasing order (lowest first) for the values of e/m for electron (e), proton (p), neutron (n) and α-particles is

• e, p, n, α

• n, α, p, e

• n, p, e, α

• n, p, α, e

A particle moving with a velocity 10⁶ m/s will have de-Broglie wavelength nearly [Given, m= 6.62 × 10^-27 kg, h =  6.62 × 10^-34 J-s]

• 10^-9m

• 10^-13 m

• 10^-19 m

• 1 Å

From the given sets of quantum numbers, the one that is inconsistent with the theory is

• n =3; l =2; m = -3; s = +$\frac{1}{2}$

• n = 4; l = 3; m = 3; s = +$\frac{1}{2}$

• n = 2; l = 1; m = 0; s = -$\frac{1}{2}$

• n = 4; l = 3; m = 2; s = +$\frac{1}{2}$

In the following particle

₃Li⁶ + ? → ₂He⁴ + ₁H³

the missing particle is

• electron

• neutron

• proton

• deuteron

Bohr's radius of 2^nd orbit of Be³⁺ is equal to that of

• 4^th orbit of hydrogen

• 2^nd orbit of He⁺

• 3^rd orbit of Li²⁺

• first orbit of hydrogen

168.

The sky looks blue due to

• dispersion effect

• reflection

• transmission

• scattering

A radioactive substance disintegrate its 90% in 100 days. How much time it will take to disintegrate its 99.9% ?

• 100 days

• 200 days

• 300 days

• 400 days

The wavelength of an electron having kinetic energy equal to 4.55 × 10^-25 J is (h = 6.6 × 10^-34 kgm²s^-1, mass of electron = 9.1 × 10^-31 kg)

• 7.25 × 10^-7 nm

• 725 nm

• 7.25 × 10^-7 m

• 7.25 × 10⁷ nm