If the radius of the 3^rd Bohr's orbit of hydrogen atom is r₃ and the radius of 4^th Bohr's orbit is r₄. Then :

The minimum energy that must be possessed by photons in order to produce the photoelectric effect with platinum metal is :

[Given : The threshold frequency of platinum is 1.3 $$\times$$ 10¹⁵ s^$$-$$1 and h = 6.6 $$\times$$ 10^$$-$$34 J s.]

The pair, in which ions are isoelectronic with AI³⁺ is :

The energy of one mole of photons of radiation of wavelength 300 nm is

(Given : h = 6.63 $$\times$$ 10^$$-$$34 J s, N_A = 6.02 $$\times$$ 10²³ mol^$$-$$1, c = 3 $$\times$$ 10⁸ m s^$$-$$1)