Understanding Work Function of Metals

What is the definition of work function?

• The work function is the minimum energy needed to remove an electron from a material's surface.

• The work function is the energy required to heat a material.

• The work function is the energy needed to create a photon from a material.

• The work function is the total energy of an electron in a material.

Explain the photoelectric effect.

• The photoelectric effect is the reflection of light off a surface, causing electrons to be emitted.

• The photoelectric effect is the absorption of light by a material without any electron emission.

• The photoelectric effect occurs only in metals when exposed to ultraviolet light.

• The photoelectric effect is the emission of electrons from a material when it is exposed to light, demonstrating the particle nature of light.

List three factors that affect the work function of a metal.

• Humidity levels

• nature of metal surface, properties of metal

• Color of the metal

• Electrical conductivity

What is the value of 1 eV in joules?

• 1.602 x 10^-19 joules

• 1.23 x 10^-19 joules

• 2.5 x 10^-19 joules

• 1.0 x 10^-18 joules

Describe three methods to determine the work function of a metal.

• X-ray Diffraction

• Three methods to determine the work function of a metal are: 1) Photoelectric Effect, 2) Thermionic Emission, 3) Field Emission.

• Chemical Analysis

• Ultrasonic Testing

What was Heinrich Hertz's observation related to the photoelectric effect?

• Hertz observed that ultraviolet light causes the emission of electrons from metals.

• Hertz found that X-rays can penetrate metals without any effect on electrons.

• Hertz noted that visible light causes metals to glow without emitting electrons.

• Hertz discovered that infrared light increases the temperature of metals.

What were the observations made by Lenard and Hallwachs regarding the photoelectric effect?

• Lenard and Hallwachs concluded that the emission of electrons was solely dependent on the color of the light.

• They found that only ultraviolet light could cause electron emission, regardless of intensity.

• • As soon as the ultraviolet radiations were stopped, the current flow also stopped. These observations indicate that when ultraviolet radiations fall on the emitter plate C, electrons are ejected from it which are attracted towards the positive, collector plate A by the electric field.

  • The electrons flow through the evacuated glass tube, resulting in the current flow. Thus, light falling on the surface of the emitter causes current in the external circuit. Hallwachs and Lenard studied how this photo current varied with collector plate potential, and with frequency and intensity of incident light.

• Lenard and Hallwachs discovered that light can increase the temperature of metals without emitting electrons.

What further studies did Hallwachs conduct, and what was his conclusion?

• Hallwachs found that light has no effect on the emission of electrons from materials.

• Hallwachs concluded that only heat can cause the emission of electrons from materials.

• Hallwachs discovered that sound can cause the emission of electrons from materials.

• Hallwachs concluded that light can cause the emission of electrons from materials.

Define threshold frequency in the context of the photoelectric effect.

• The threshold frequency is the minimum frequency of light needed to initiate the photoelectric effect.

• The threshold frequency is the frequency of light that can only heat a material without causing electron emission.

• The threshold frequency is the frequency at which electrons are emitted regardless of light intensity.

• The threshold frequency is the maximum frequency of light that can cause the photoelectric effect.

which are the metals yhat are sensitive to visible light ?

• Li,Na,K,Cs,Rb

• Zn,Mg,Cd

• H2,O2,Hg

• Xe,Kr,Pt,Ni