A 100-watt bulb emits monochromatic light with a wavelength of 400 nm.
How many photons does it emit every second?
1. \(40.12 \times 10^{20} \ s^{-1}\)
2. \(2.012 \times 10^{21} \ s^{-1}\)
3. \(2.012 \times 10^{20} \ s^{-1}\)
4. \(20.12 \times 10^{21} \ s^{-1}\)

When electromagnetic radiation of wavelength 300 nm falls on the surface of sodium, electrons are emitted with a kinetic energy of 1.68 ×10⁵ J mol^–1. The minimum energy needed to remove an electron from sodium and the maximum wavelength that will cause a photoelectron to be emitted are, respectively:

1. 2.31 × 10⁵ J mol^–1, 517 nm

2. 23.1 × 10⁵ J mol^–1, 517 nm

3. 3.31 × 10⁵ J mol^–1, 417 nm

4. 33.1 × 10⁵ J mol^–1, 417 nm

The threshold frequency ν_o for a metal is 7.0 ×10¹⁴ s^–1. The kinetic energy of an electron emitted when radiation of frequency ν =1.0 ×10¹⁵ s^–1 hits the metal, is-

1. 19.88 ×10^–19 J

2. 1.988 ×10^–19 J

3. 1.988 ×10^–20 J

4. 19.88 ×10^–17 J

The frequency and wavelength of a photon emitted during a transition from n = 5 state to the n = 2 state in the hydrogen atom  are respectively :

1.  \(6.91\times10 ^{14} Hz\);   543 nm

2. \(7.91\times10 ^{14} Hz\); 434 nm

3. \(6.91\times10 ^{14} Hz\); 434 nm 

4. \(7.91\times10 ^{14} Hz\); 343 nm

The energy and the radius of the first orbit of He⁺ are respectively :

1. \(-8.72\times 10^{-18}J\); 0.02645 nm

2. \(8.72\times 10^{-18}J\); 0.02645 nm

3. \(-7.82\times 10^{-18}J\) ; 0.03655 nm

4. \(7.82\times 10^{-18}J\); 0.03655 nm

Find the de Broglie wavelength of a ball of mass 0.1 kg moving with a velocity of 10 m s⁻¹.

1. 662.6 × 10^–34 m

2. 66.26 × 10^–34 m

3. 6.626 × 10^–34 m

4. 6.626 × 10^–36 m

The mass of a photon with wavelength 3.6 Å is :

A microscope using appropriate photons is employed to locate an electron in an atom within a distance of 0.1 Å. Calculate the uncertainty involved in the measurement of its velocity:

A golf ball has a mass of 40g, and a speed of 45 m/s. If the speed can be measured within the accuracy of 2%, the uncertainty in the position is:

1. 14.6×10^–23 m

2. 14.6×10^–33 m

3. 1.46×10^–23 m

4. 1.46×10^–33 m