PHYSICS

*Waves and sound*

A wave is a disturbance that travel outward from a source and it carries energy along with it .

* Transverse wave: it travels in a direction  perpendicular to the source eg

Water waves
X-ray
All electromagnetic aves

Longitudinal waves : It travel in a direction that is parallel to the source Eg

Sound waves

Mechanical wave need material medium foR its propagations
Eg  sound waves water wave and string waves


Electromagnetic waves does not require material medium

✅Crest : highest point on waves

✅ Through: lowest point on waves

✅ Amplitude: Maximum particle displacement

✅ Frequency: number of complete vibration per second (f)

✅ period: time taken to complete a vibration (T)

✅ Velocity : displacement through which wave is propagated in one secs (v)

✅ formulas

* F=1/T
*V= f x wavelength
*V= wavelength ÷ T


✅ *Properties of waves*

*Reflection
*Refraction
*Diffraction
*Interference

*Polarization: this is a process of making waves to move in one direction

Polarization is applicable to transverse wave only


✅ Longitudinal waves are never polarized eg sound waves


✅Sound waves can travel in all states of matter but with different speed

The speed of sound is dependent on vibration of particles and thus the closer the particles the faster sound moves.

Air= fast
Liquid= faster
Solid= fastest
Eg this explain why sound travel far and fast when using trumpet.

✅ Sound wave is not affected by gas pressure

✅ Speed of sound increases with temperature

✅ V=2d÷t

*v= velocity or speed
*d= distance
*t= time
The above formula is relevant in calculation for speed of sound.

✅ *Light waves*


G-gamma ray
X-ray
U-ultraviolet radiation
V- visible light
I- infrared ray
M- microwaves
R- Radio waves

✅ Visible light is an electromagnetic component

✅ light travels through metal water and vacuum

✅ Ray: path in which light travel


✅Beam; collection of ray

✅ Rectilinear propagation of light : when light travels it cast shadow on object placed along its path

✅ Umbra : total shadow

✅ Penumbra : partial shadow

*Eclipse*


✅ Eclipse of sun: this occurs when moon comes between earth and sun, then moon cast shadow on earth


✅ Lunar eclipse: this occurs when the earth comes between the moon and the sun then earth cast shadow on moon.

✅ *pin hole camera*


✅ the image is inverted and clear if the hole is very tiny

✅ if the hole is too big then the image appear blurr


✅ *Laws of reflection*

*The incident ray the reflected ray and the normal all lies in the same plane

*Angle of incidence = Angle of reflection

✅ *Nature of image formed by plane mirror*

*Virtual: cannot be seen on screen
*Erect but laterally inverted
*Same size as object
*The distance between the object in front of the mirror and image behind the mirror are the same.

✅ *inclined mirror*

When two plane mirror  are inclined to each other at an angle©to each other then N= number of images produced

N={360֩} -1
Example

How many images are formed when 2 mirrors are inclined at Angle 30°

Solution:

N= (360÷30) - 1
N= 12-1
N= 11

The number of images = 11

✅ Uses of plane mirror
*Kaleidoscope

*Sextant: instrument used in measuring angle of elevation of the sun

*Simple periscope

*Looking glass

*Overhead projector


✅ *Nature of image of convex mirror*

Regardless of the position of the object, it is always

Diminished
Erect and
Virtual

.Summary of today's session


*PHYSICS TIPS*

✅Fundamental quantities

*Length (m)
*Mass (kg)
*Time (s)
*Electric current (A)
*Temperature (K)


✅Derived quantities

*Area
*Volume
*Density
*Speed
*Force
*Pressure
*Energy
*Charge
*Momentum
*Impulse

*SCALAR VS VECTOR QUANTITY*


✅SCALAR :These are physical quantities with magnitude but no direction

*Length
*Mass
*Time
*Speed
*Pressure
*Electric potential
*Altitude
*Potential difference
*Power
*Electric current
*Energy (kinetic & potential)
*Heat capacity

✅Vector: These are quantities with both magnitude and direction.

*Displacement
*Acceleration
*Velocity
*Force
*Impulse
*Momentum
*Acceleration due to gravity
*Magnetic induction
*Electric field intensity


✅ *DIMENSION:THIS ARE PHYSICAL QUANTITIES INVOLVING MASS-LENGHT-TIME*

Mass: M
Length :L
Time : T or change in time

*Force: M x L x T^-2

*Pressure : Force /Area = F ÷ L^2

*Work or Energy F x L



✅ Measurement

*Meter rule= 1.0
*Vernier caliper = 1.00
*Micrometre screw gauge= 1.000


✅ Force  and examples

Contact force : this must come in touch with the body to take effect eg

*Tension
*Reaction
*Thrust
*Upthrust
*Surface tension

Field force : does not need to come in contact
Eg

*Electrostatics
*Gravitational
*Magnetic


✅ Temperature and its measurement

°C ->K = X + 273
°C-> °F = 32 + 1.8 (x°c)
°F-> °C = (x°f) - 32 x 0.556

Examples convert the following

# 27°c to Kelvin
# 30°c to °F
# 50°F to °C

Solutions

27°c to kelvin = 27 + 273= 300K


30°c to °F
 = 32+ 1.8 (30°c)
=32+ 54
=86°F

50°f to °c
= (50°f) - 32 x 0.556
= 18 x 0.556
= 10.08~ 10



✅ Average kinetic energy of water is highest in steam and this causes serious burn to the skin due to the specific heat of vaporization of steam

✅ Temperature is the measure of average kinetic energy of molecule

✅ Low temperature less collision of molecules and vice versa


✅ Density of gas depend on separation between its molecules

✅Concrete floor feels colder because its a better heat conductor


✅Conduction : Heat transfer as a result of vibration of molecules

✅ Convection: heat transfer as a result of motion between molecules.


✅ Radiation: Heat transfer without material medium


✅ Black body radiates heat most and losses heat readily


✅White or Bright color cloth is the best to wear in sunny day to feel cool : it doesn't conduct much heat.

✅ Radiation is not applicable to molecular theory of gas

*Thermoflask*

It prevent heat lost due to conduction convention and radiation

*Conduction*

1- Evacuated space between the Walls
2- cover cork of low thermal conductivity

*Convection*

Evacuated space between the walls

*Radiation*

1- Evacuated space between the walls

2- The wall is coated with Silver

✅ Diffusion occur in solid liquid and gas

* Gas =fastest
*Liquid = moderate
*Solid = slow

✅ *Electrostatics*

This simply means charge in motion.

*An electron has a charge of 1.6x10^-19C


✅ Electric field: Region in which electric force is being felt


✅Capacitor : A device that stores electric charge

✅ Capacitance: this is the ability of a capacitor to store electric charge
C=Q/V


✅ Capacitance depend on :
*Area of plate
*Distance between the plate
*Nature of material between the plate.


✅ *Arrangement of capacitor*

Series:
       c1.   c2.   c3
  ----|  |----|  |----|  |----

1/C= 1/c1 + 1/c2 + 1/c3

Parallel :

 ---------|c1|-----------
 ---------|c2|-----------
--------- |c3|-----------

C= C1 + C2 + C3


✅ Convex : Diverging mirror

✅ concave : Converging mirror

✅ A man walk towards a plane mirror at speed of 2m/s along the direction of normal to the mirror, his image moves towards him at what speed.

Solution :

Image speed = 2× object speed.

Image speed = 2 x 2m/s

Image speed = 4m/s

The image moves towards him at a speed of 4m/s.



✅ If a ray of light passes through the centre if curvature it will have an angle of 0°.

✅ *Refraction of light*

*Refraction: this is a process by which light bend when it travels from one medium to another.

✅ Refractive index : this is the ratio of speed of light in two media of different density.

✅ Refractive index of H2O = Speed of light in Air ÷ speed of light in H2O

*Refractive index = Π
*Speed of light in Air = ∆Air
*Speed of light in H2O = ∆H2O

 ✅ The speed of light in air is 3x10^8 and refractive index of H2O is 4/3 find the speed of light in H2O.

Solution:

(4/3)= 3x 3x10^8 ÷ ∆H2O

∆H2O= 3x 3x10^8 ÷ 4

∆H2O= 9 x 10^8 ÷ 4

∆H2O= 2.25 x 10^8


✅ Speed of light in glass medium is 1.8x 10^8, if the speed of light in air is 3 x10^8 . find the refractive index of glass.

Solution:
Πglass = ∆Air ÷ ∆glass

Πglass = 3x10^8 ÷ 1.8x 10^8

Πglass= 3÷1.8
Πglass= 1.667



✅ *Dispersion of white light*

R-Red
O-Orange
Y-Yellow
G-Green
B-Blue
I-Indigo
V-Violet

✅Red is the highest and speed decreases downward.


✅ Red has the lowest deviation which increase downward

✅ Red has the lowest refractive index which increase downward


✅       *Electromagnetic waves*

*All electromagnetic waves are transverse waves.


✅ Electromagnetic waves that can be detected by heat is X-ray

✅ Overlapping : means impurity of colour spectrum

✅How to obtain pure spectrum
From source to the screen

          [Source]
               |
            SLIT
               |
            CVL
               |
          PRISM
               |
            CVL
               |
        SCREEN

*CVL= CONVERGING LENS

* triangular prism

 The light is allowed to pass through all the above to become pure. possible at high temperatures✅ *Magnetism and Electromagnetism*


✅ A magnet is a material that attract metal

When a magnet is suspended it point to the north-south direction

✅ Magnet can be made in two ways

*Electrically with the aid of solenoid

*Mechanically by stroking

✅ *Magnetic property*

*Soft iron is easily magnetized than steel

*soft iron losses magnetic property easily

*Soft iron is the best material for temporary magnet due to the above property

✅ *Demagnetization*

*Heating to redness and allowing it cool in E-W direction

*Beating with hammer in E-W direction

*Putting in solenoid in E-W direction and passing alternating current through

✅ Magnetic field: region in which magnetic effect is being felt.

✅ Magnetic field strength or magnetic flux : this is the measure of magnetic force.


✅ *Earth as a giant magnet*

✅ Magnetic meridian: North and south pole of the earth

✅ Angle of declination: Angle between the magnetic and geographic meridian

✅Angle of dip: Angle which the axis of the magnet makes with the horizontal

✅ strength of electromagnet can be increased by:

*Increasing the no of winding or turns

*Current increase

*Reduce distance between magnet


✅ Non magnetic material

* Brass
*Glass
*Copper
*Lead


✅ To convert an Ac generator to DC generator ( Slip rings are changed to split ring)

A commutator made of split ring changes Ac to DC

✅ Parts of Ac generator

*Carbon brushes
*Field magnet
*Slip rings✅ *Modern physics*

*Themoionic emission : this occurs when a piece of metal is placed in a vacuum and heated so it causes emission of electron from the metal surface.

✅ Photoelectric emission : when light of appropriate frequency is allowed to fall on a metal surface, electrons are knocked off the surface .

✅ *Energy of quantum radiation*

*E=hf

h= planks constant (6.63x10^-34)J/s

f= frequency

E= energy of radiation

E=hf=W+1/2 mv^2

W=minimum energy needed to remove electron from the metal surface (work function)

1/2 MV^2 = kinetic energy of electron  (K.e)


✅ A metal has work function of 5.76ev is illuminated with radiation of 7.88ev what is the kinetic energy of the electron

Solution;

E=hf=W+1/2mv^2

E=W+1/2mv^2

For simplicity change 1/2mv^2 to k.e

E=W+ke

E=7.88ev
W=5.76ev
Ke=x

7.88ev= 5.76ev + ke

Ke= 7.88 - 5.76

Ke = 2.12ev



✅  x-ray

Properties:
*it can penetrate materials of considerable thickness

*Can be detected by photographic plate

Uses:

*For capturing skeletal structure
*For detecting leakage in pipe
*For studying structure of crystals (crystallography)

✅ Cathode ray:

*consist of negative charge
*causes fluorescence
*produce electromagnetic ray.


✅✅✅ The number of electron removed from metals surface depend on light intensity

✅✅✅ The kinetic energy of electron from the metal surface depend on
*wave lenght of light
*Nature of the surface

✅ Application of photoelectric emission
*Photograph light meter
*Used in automatic door
*Burglar alarm
*produced sound from film track
✅ calculating power

Energy per unit time

P=E/t
P=IV
P=V^2/R .( v= voltage and R = resistance)
P=I^2 x R ( I= current)

✅ The reading of pressure on mercury tube depend on

*Area of tube
*Density of mercury
*Temperature of mercury
*Acceleration due to gravity



But has nothing to do with Atmospheric pressure of the tube

✅ intrinsic or internal property of a material .

* Resistance
*Resistivity

✅ An electric heater convert electric energy to heat energy at 1kj in every 2 seconds with efficiency of 100% find the power


Solution :

Remember power is the rate at which work is done or energy is dissipated .

P=E÷t

P=power
E=energy
t=time

P=1kj÷2seconds
P= 1÷2
P=0.5 kj/s or Watt

✅ energy of photo emissions depend on frequency
✅ in resonance Xc=Xl

Capacitance= inductance

And also

Z=R

Impedance=Resistance

✅ An element an its isotope differ by number of neutron

✅ when electron from heated filament accelerate through a vacuum towards positive plate : electromagnetic waves will be produced

✅ Latent heat: either of vaporization (steam) or fusion (ice block) is the heat supplied or removed which causes change of state without any change in temperature

✅ Thermostat that regulate the amount of heat in electrical appliances eg iron cooker etc is made of bimetallic strip
✅ Overhead cable or wire are usually allowed to sag so as to create a balance during change in temperature.

When temperature is high the cable expand and it becomes longer


When temperature is low the wire contracts and it becomes shorter

The wire is left to sag so that when the temperature is lower and the wire becomes shorter it wont be stretched excessively which can cause damage.

So wire are left to sag so as to adapt with drop in temperature of the environment.

✅ Operation of hydraulic jack is based on pascals principle.

Operation of spiral spring is based on hook's law