When electromagnetic radiation of wavelength 300 nm falls on the surface of a metal, electrons are emitted with the kinetic energy of 1.68 × 10⁵ J mol^–1. The minimum energy needed to remove one mole of electron from the metal is: 

(h = 6.626 × 10^–34 Js, c = 3 × 10⁸ ms^–1, N_A = 6.022 × 10²³ mol^–1)

1.  2.31 × 10⁶ J mol^–1
2.  3.84 × 10⁴ J mol^–1
3.  3.84 × 10^–19 J mol^–1
4.  2.31 × 10⁵ J mol^–1

A monochromatic infrared range finder of power 1milli watt emits photons with wavelength 1000 nm in 0.1 second. The number of photons emitted in 0.1 second is:
(Given: h = \(6.626 \times 10^{-34} J~s\) , c = \(3 \times 10^8 m~s^{-1}, \) Avogadro number = \(6.022 \times 10^{23}\))

1. \(30 \times 10^{37}\)
2. \(5 \times 10^{14} \)
3. \(30 \times 10^{34} \)
4. \(5 \times 10^{11} \)

Which one of the following electrons in the ground state will have least amount of energy?