The threshold energy for photoelectric emission of electrons from a metal is 3.056 × 10 - 15 joule. If light of 4000 Å wavelength is used, will the electrons be ejected or not? h = 6.63 × 10 - 34 Js .

Threshold energy, W = 3.056 × 10 - 15 J G i v e n Thus, wavelength of incident light, λ = 4000 Å = 4 × 10 - 7 m We know, E = h c λ where, h = 6.63 × 10 - 34 J s and c is the speed of light = 3 × 10 8 m / s Thus, E = 6.63 × 10 - 34 × 3 × 10 8 4 × 10 - 7 = 4.9725 × 10 - 34 + 15 J = 4.9725 × 10 - 19 J We can see that threshold energy W is greater than the Energy of incident light E , therefore electron will not be ejected.

E M B I B E

Pradeep's Chemistry Vol 1>Chapter 2 - Structure of Atom>PROBLEMS FOR PRACTICE>Q 4

MEDIUM

11th CBSE

IMPORTANT

Earn 100

Light of wavelength $4000 Å$ falls on the surface of caesium. Calculate the energy of the photoelectron emitted. The critical wavelength for photoelectric effect in caesium is $6600 Å$ .

Important Questions on Structure of Atom

HARD

11th CBSE

IMPORTANT

Pradeep's Chemistry Vol 1>Chapter 2 - Structure of Atom>PROBLEMS FOR PRACTICE>Q 5

What is the ratio between the energies of two radiations, one with a wavelength of

6000 Å

and the other with

2000 Å [1 Å = 10^{- 10} m] ?

MEDIUM

11th CBSE

IMPORTANT

Pradeep's Chemistry Vol 1>Chapter 2 - Structure of Atom>PROBLEMS FOR PRACTICE>Q 6

The threshold energy for photoelectric emission of electrons from a metal is

3.056 \times 10^{- 15}

joule. If light of

4000 Å

wavelength is used, will the electrons be ejected or not?

(h = 6.63 \times 10^{- 34} Js) .

MEDIUM

11th CBSE

IMPORTANT

Pradeep's Chemistry Vol 1>Chapter 2 - Structure of Atom>PROBLEMS FOR PRACTICE>Q 7

Calculate the wavelength of a photon in Angstrom units having energy of one electron volt.

MEDIUM

11th CBSE

IMPORTANT

Pradeep's Chemistry Vol 1>Chapter 2 - Structure of Atom>PROBLEMS FOR PRACTICE>Q 8

Sodium street lamp gives off a characteristic yellow light of wavelength

588 n m .

Calculate the energy per mole

(i n k J / m o l)

of these photons.

MEDIUM

11th CBSE

IMPORTANT

Pradeep's Chemistry Vol 1>Chapter 2 - Structure of Atom>PROBLEMS FOR PRACTICE>Q 1

Calculate the frequency and the wavelength of the radiation in nanometers emitted when an electron in the hydrogen atom jumps from third orbit to the ground state. In which region of the electromagnetic will this line lie? (Rydberg constant