Bohr Model of Atom, Energy Level, Hydrogen Spectrum (NEET LEVEL)

1.

A gas of hydrogen like atoms can absorb radiations of 68 eV. Consequently, the atoms emit radiations of only three different wavelengths. All the wavelengths are equal or smaller than that of the absorbed photon.

(a)

Determine the initial state of the gas atoms.

(a) 28.5 Å

(b) 46.3 Å

(c) 1.7 Å 

(d) 3.4 Å 

Ans (a)

(b)

Identify the gas atoms.

(a) n = 2,   Z = 9

(b) n = 2,   Z = 1

(c) n = 2,   Z = 2

(d) n = 2,   Z = 6

Ans (d)

(c)

Find the minimum wavelength of the emitted radiations.

(a) 25.32 Å ,

(b)  0.76 Å

(c) 2.3 Å

(d) 12.3 Å

Ans (a)

(d)

Find the ionization energy and the respective wavelength for the gas atoms.

(a) 450.2 eV

(b) 489.6 eV

(c) 328.4 eV

(d) 423.5 eV

Ans (b)

2.

A 100-W bulb converts 5% of the electrical energy input to visible light. Assume the light has a wavelength of 600 nm and the bulb is a point source.

(a)

What is the number of photons emitted per second?

(a) 1.51 x 10¹⁹s^-1

(b) 0.51 x 10¹⁹s^-1

(c) 4.51 x10¹⁹s^-1

(d) 9.51 x10¹⁹s^-1

Ans (a)

(b)

If the eye can detect 20 photons/s, at what distance would the bulb be visible? Take the pupil diameter to be 3 mm.

(a) 700 km

(b) 38 km

(c) 150 km

(d) 652 km

Ans (d)

3.

A hydrogen atom emits radiation of wavelength 102.5 nm. What are the n values of the two levels involved?

(a) n = 1, 1

(b) n = 1, 3

(c) n = 1, 2

(d) n = 1, 9

Ans (b)

4.

The electron in the hydrogen atom is in the n = 2 state. What is its

(a) potential energy

(a) – 6.8 eV

(b) – 6.2 eV

(c) – 7.4 eV

(d) -2.5 eV

Ans (a)

(b)

kinetic energy?

(a) 0.3 eV

(b) 3.4 eV

(c) 9.2 eV

(d) 11.5 eV

Ans (b)

5.

What is the maximum wavelength that can ionize a hydrogen atom in the ground state? In what region of the electromagnetic spectrum does this wavelength lie?

(a) 20.5 nm

(b) 55.3 nm

(c) 73.9 nm

(d) 91.2 nm

Ans (d)

6.

What is the shortest wavelength

(a)

in the Balmer series

(a) 2000 Å

(b) 3050 Å

(c) 3650 Å

(d) 4000 Å

Ans (c)

(b)

in the Lyman series?

(a) 914 Å

(b) 948 Å

(c) 1000 Å

(d) 2000 Å

Ans (a)