An external force can change a body's length, shape, or volume, so deformation may occur in any of these.

23 days ≈ 2.86 half-lives, so activity = 600*(1/2)^{23/8.04} ≈ 83 Bq, which is a little more than 75 Bq.

Photon carries momentum p = E/c with E from n=6 to n=1 transition; recoil velocity v = p/m_H ≈ 4.2 m/s, matching option B.

Half-life is an intrinsic property of a radioactive isotope and is independent of external conditions such as pressure or temperature.

Alpha particles are positively charged and experience a force in the direction of the electric field vector, so they deflect along the field.

Deuterium commonly refers to the hydrogen atom with one neutron, while triton refers to the hydrogen nucleus with two neutrons, matching atom and nucleus of hydrogen respectively.

Planck's constant has units of action (energy × time), which are equivalent to angular momentum.

Electron count sums to 18 (so Z=18 protons); with A=40, neutrons = 40-18 = 22, so option A (22 neutrons, 18 protons) is correct.

Overlap of valence and conduction bands allows free carrier motion characteristic of metals.

The n=3 to n=2 transition in hydrogen corresponds to H-alpha with wavelength ~656 nm, giving frequency ≈ 4.6 × 10¹⁴ Hz.