Photoelectric Effect [ Light is a PARTICLE]

In the previous entry, we said that light is a WAVE based on its characteristics of showing wave phenomena. Knowing that, light is also a PARTICLE. Later in this writing, we will figure out how light can be also concluded as a particle.

Photoelectric Effect

Photoelectric Effect is the emission of electrons (called photoelectrons) from a metal surface when an incident light strikes the surface with enough energy/frequency.

The photoelectric effect is represented by the Einstein's Photoelectric Effect equation:

This equations consists of 3 terms which represent 3 items in the figure above that are , E is for the incident light , Wo is for the Metal and Kmax is for the Photoelectrons.

The incident light energy must be bigger than the work function of the metal. Work function is basically the energy possessed by the electrons in the metal. Hence, to free these electrons from the metal , the incident light must have enough energy to displace the electrons.

The incident light frequency must be bigger than the threshold frequency. threshold frequency is basically the frequency possessed by the electrons in the metal (electrons vibration). Hence, to free these electrons from the metal , the incident light must have enough frequency to displace the electrons.

Light as a particle

By the Photoelectric Effect experiment, Einstein found out that light that strikes the metal with different frequency will either emits or does not emit electrons from the metal surface. If we have blue and red light of the same brightness strike the metal, red light gives off no electrons! Why? This is because red light has lower energy (due to its lowest frequency).

It is proven that light cannot behave as a wave in this case!!! If it is a wave, the emission of photoelectrons will depends on the amplitude of wave (incident light) as the amplitude is directly proportional to energy.

The physicist Max Planck suggested that light comes in a discrete bundle, called quanta (PARTICLE). Then, Einstein suggested that each quantum (singular of quanta) of light has enough energy to escape one electron from the metal. This light particle is named as PHOTON. The emission of the photoelectrons does not depend on how many photons (light) strikes the metal but it depends on the energy brought by each photon.

Thank you,
Mdm Ummi Atiah KMPk

~ May it Benefits You ➽💕

Comments

Electric Potential

Electric Potential, V If Ali wants to move his charge towards the charged sphere on the left, he has to push against the repulsive force between the two spheres (because both are positively charged) Ali is actually doing work (when he push) , Remember W= f.s ! At the same time, Ali's charge gains electric potential energy . If Ali let go his charge, it will move away from the sphere, it looses electric potential energy. The electric potential at a point is telling us the potential energy of each coulomb of charge . When you move a charge in an electric field its potential energy changes. This is analogous to moving a mass in a gravitational field. Electric potential is a scalar quantity. Thank you, Mdm Ummi Atiah KMPk ~ May it Benefits You ➽💕

Root Mean Square Current (I rms)

Root Mean Square Current As mentioned in the previous post , the value of AC is always changing. Then, how do we measure its value??? We could not use the maximum value of the current Io, because it only occurs at a moment. The average current is ZERO . Hence, one effective value that we could use the root mean square value. Irms . The formula for Irms is given by: where Io is maximum current. Irms is the value that is equivalent to a steady direct current . We can investigate this by comparing 2 circuits containing lamp each. circuit 1 uses battery as the source, while circuit 2 uses a.c. supply. AC supply is adjusted so that both lamps are equally bright. At this point, DC and AC supplies are transferring energy to the lamps at the same rate (Power). By equating the Power of both circuits, we can deduce the equation of Irms as above. Therefore, the d.c. voltage equals the r.m.s. value of the a.c. voltage. From the the graph below and th...

Magnetic Field

Magnetic Field, B To define Magnetic field, we start with the word field. Field means a region or space. The magnetic field is defined as a region where the magnetic force can be felt. In other words, a force (repel/attract) can be felt in the region. Bar Magnet We will find that 2 North(N) poles will repel if we bring the poles of two bar magnets together. Same goes to that of 2 South(S) poles. However North and South pole attracts. The strength and direction of the field are represented by lines. Knowing that, the direction of magnetic field is from North to South. Magnetic field is able to be detected by 1) Compass (have been used over 2000 years 2) Hall Probe Applications: Swipe cards, Video tapes & Computer discs -use magnetism to store information. History: In 1819, Hans Christian Oersted noticed that a compass needle was deflected by an electric current in a nearby wire. Remember!! the compass is used to detect any existance of magnetic field. By th...

Think Like A Proton, Always Positive :)

Search This Blog