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Question:
Explain photoelectricity

Answer:
Photoelectricity is a phenomenon by which the incidence of light or electromagnetic radiations of appropriate frequency or wavelength on the surface of a clean metal brings about the emission of photoelectrons.

Question:
how is photoelectricity related or not to thermionic emission?

Answer:

Photoelectricity
Photoelectricity is a phenomenon by which electrons are emitted from the surface of a clean metal when light or electromagnetic radiations of appropriate frequency or wavelength is incident on the surface of the metal.
Thermionic emission
This refers to the emission of ions from the surface of a metal when it is strongly heated to a certain degree.

Similarities
In both, metal is involved

Differences between photoelectricity and thermionic emission
1. In photoelectricity, electrons are emitted while ions are emitted in the case of Thermionic emission.
2. Incidence of light of appropriate frequency or wavelength brings about photoelectricity while heat is involved in thermionic emission.

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Question:
What are the differences and similarities between distance and displacement
Answer
Of the most confusing terms in physics are the two above (i.e distance and displacement) terms are used to mean the same thing but there are distinctions between them especially when dealing with linear motion.
Distance is the separation between two points or the gap between any two positions in space. e.g if a person moves from a poiunt P to a point Q, the distance moved by the person would be the length PQ.
It is a scalar quantity(as such it has only magnitude but no direction) measured in metre(m).
Displacement is the distance moved in a specified direction (i.e on a straight line). It is the distance moved by an object from its initial position to its final position.
It is a vector quantity measured in metre(m).
DIFFERENCES BETWEEN DISTANCE AND DISPLACEMENT
Distance is a scalar quantity while displacement is a vector quantity.
Distance requires only magnitude to be specified while displacement requires not just magnitude but also direction to be specified i.e. if you say the distance moved by a person is 50m, then you have completely stated the distance moved by the person. But if you say the displacement of a body is 10m, you have not completely stated the displacement of the body, you have only stated the magnitude(size) of the displacement of that body.
SIMILARITIES BETWEEN DISTANCE AND DISPLACEMENT
Both distance and displacement are measured in metre (m).
Both are denoted by “s”
Both quantities have magnitude
NOTE: the distance moved by a body in a straight line is equal in magnitude to the displacement of the body.

ELECTRICITY 1
CURRENT ELECTRICITY
CURRENT
Current (I) is the rate at which electric charges flow through a conductor.
It can be measured using an ammeter or milliameter (for small currents).
It unit is ampere (A)
It is the expression of the quantity of charges flowing through a conductor per seconds.
Mathematically, it is expressed as
Current, I = Charge, Q / Time, t
i.e I=Q/t
Hence,
1 ampere is defined as a coloumb of electricity per seconds and 1 coloumb as the quantity of electricity passing through a conductor in a second when the current flowing through it is 1 ampere.
To make calculations easier and convenient, the use of submultiples have been introduced
e.g instead of writing 0.000001A or 0.001A one can write 1µA (1 microAmpere) or 1mA (1 milliAmpere)
Where micro, µ= 1 × 10-6 or 0.000001
milli, m= 1 × 10-3 or 0.001
A sensitive ammeter is one that can measure very small current.
An accurate ammeter is one whose measurement is close to the actual value of the current.