In the following nuclear reaction,

$$D\buildrel \alpha \over \longrightarrow {D_1}\buildrel {{\beta ^ - }} \over \longrightarrow {D_2}\buildrel \alpha \over \longrightarrow {D_3}\buildrel \gamma \over \longrightarrow {D_4}$$

Mass number of D is 182 and atomic number is 74. Mass number and atomic number of D₄ respectively will be _________.

The activity of a radioactive material is 2.56 $$\times$$ 10^$$-$$3 Ci. If the half life of the material is 5 days, after how many days the activity will become 2 $$\times$$ 10^$$-$$5 Ci ?

Let K₁ and K₂ be the maximum kinetic energies of photo-electrons emitted when two monochromatic beams of wavelength $$\lambda$$₁ and $$\lambda$$₂, respectively are incident on a metallic surface. If $$\lambda$$₁ = 3$$\lambda$$₂ then :

Following statements related to radioactivity are given below :

(A) Radioactivity is a random and spontaneous process and is dependent on physical and chemical conditions.

(B) The number of un-decayed nuclei in the radioactive sample decays exponentially with time.

(C) Slope of the graph of log_e (no. of undecayed nuclei) Vs. time represents the reciprocal of mean life time ($$\tau$$).

(D) Product of decay constant ($$\lambda$$) and half-life time (T_1/2) is not constant.

Choose the most appropriate answer from the options given below :