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# Lesson Note on Physics SS2 Third Term

## SCHEME OF WORK

WEEK 1: GLASS PRISM

WEEK 2: LENSES

WEEK 3: OPTICAL INSTRUMENTS

WEEK 4: OPTICAL INSTRUMENTS

WEEK 5: DISPERSION OF WHITE LIGHT

WEEK 6: DISPERSION OF WHITE LIGHT

WEEK 7: SOUND WAVES

WEEK 8: SOUND WAVE

WEEK 9: RESONANCE

# Below are the 2022 complete Physics lesson notes for SS2 Third Term

Week 1

## Spectrum from prism

Sunlight is often called white light since it is a combination of all visible colours. Since the index of refraction is different for each color, the angle of refraction will be different for each color when the light passes from air into glass or other transparent material. This is according to Snell’s Law.

Now if the piece of glass has parallel sides, such as with a window, the light will return in the same direction that it entered the material. But if the material is shaped like a prism, the angles for each color will be exaggerated, and the colors will be displayed as a spectrum of light.

Week  2

Topic: LENSES

The reflection and refraction we have dealt with so far have focused only on light interacting with flat surfaces. Lenses and curved mirrors are optical instruments designed to focus light in predictable ways. While light striking a curved surface is more complicated than the flat surfaces we have looked at already, the principle is the same. Any given light ray only strikes an infinitesimally small portion of the lens or mirror, and this small portion taken by itself is roughly flat. As a result, we can still think of the normal as the line perpendicular to the tangent plane. To learn more, click here

week  3

Topic: OPTICAL INSTRUMENTS

Magnifiers

Perhaps the simplest optical instrument is the lens magnifier. Without optical aid, we cannot “see” things close up. The eye will simply not focus closer than about 0.25 m (unless you are nearsighted!). But an object placed just inside the focal point of a converging lens will produce a large virtual image that can be viewed more easily. Let’s look at our Convex Lens again.

Her we can see that the ratio of the heights of the subject and image, the magnification M is

M = hi/hs = i/s

The four basic kinds of optical instruments—the only instruments are concave mirrors, convex mirrors, convex (or converging) lenses, and concave (or diverging) lenses. If you have trouble remembering the difference between concave and convex, remember that, like caves, concave mirrors and lenses curve inward. Convex lenses and mirrors bulge outward. To learn more, click here

week  4

Topic: Optical Instruments

Optical instruments process light waves to enhance an image for viewing or analyze light waves to determine number of characteristic properties. The very first optical instruments were telescopes and microscopes used for magnifications of images. Mirrors and lenses find their applications in very many walks of life. Since the days of Galileo, these optical instruments have been greatly improved and extended into other portions of the electromagnetic spectrum. These instruments employ calculations of positions of objects and images from ray diagrams that we have discussed in Spherical Mirrors and Lenses.

Some optical instruments that we see in everyday lives are:

The human eye – convex lens.

Corrections of defects of vision – combinations of concave and convex lenses.

Compound microscope – double convex lens.

WEEK 5

TopicDISPERSION OF WHITE LIGHT

INTRODUCTION

Dispersion is the splitting up of white light into seven colours on passing through a transparent medium like a glass prism. When a white light beam is passed through a prism, a band of seven colours are formed is known as a spectrum of white light. The seven colors in the spectrum are red, orange, yellow, green, blue, indigo and violet respectively.

Dispersion of Light through Prism

The formation of spectrum of seven colors shows that white light is a mixture of seven colours (or seven coloured light). The effect of a transparent medium (like a glass prism) is only to separate the seven colors of white light. To learn more, click here

WEEK 6

TopicDispersion of White Light: Colours and Paints

Forms of Colours

1. Primary colours: There are three forms of colours or spectrum which cannot be produced by mixing any colour together. The primary colours are red, green and blue. They occur naturally from the spectrum and they can form other colours when mixed in the same proportion.

2. Secondary colours: There are colours formed from primary colours. They are colours obtained by mixing two of the primary colours together in the same proportion, e.g. when light mixes with blue light, they produce magenta colour, also when blue is mixed with green light, they produce cyan and when a green light is mixed with red light they produce yellow light.

Red + Green → Yellow

Green + Blue → Cyan

WEEK 7

TopicSOUND WAVES I

SOUND WAVES

We know that waves are the produced disturbance which are formed by vibration and travel through a medium. There are different types of waves like transverse, longitudinal waves, etc. even whatever we hear that sound also comes in the form of a wave. So, we can say that sound comes towards us in the form of a wave.

The sound waves are mechanical waves which are created from vibrations between the particles of the medium. When it is moved through the medium of air then the air particles are displaced by the moving energy of sound waves and wave is travelled. But it can also be a longitudinal wave-like in vibrating tuning fork which creates waves from vibrations.

But what type of wave is sound? How it is travelled from one medium to another medium? Is it a mechanical wave or longitudinal wave or pressure wave? Here we are given a complete explanation of these questions. Let’s discuss a detailed description on the sound waves. To learn more, click here

WEEK 8

Topic: SOUND WAVES II

Effect of Temperature and Pressure on Velocity of Sound

Velocity of Sound Waves

Since there are three states of matter, it means there must be three velocities for the three states, because experimentally three states are not the same. The velocity varies from medium to medium.

The velocity of sound in air, for dry air at 00C is approximately 330m/s, but at room temperature, it is about 340m/s, approximately used in the calculation as 330m/s.

The velocity of sound in water, i.e, liquid state is about 1,500m/s, approximately about 4 times the velocity of sound in air. For example, steel is in a solid state. The velocity of sound in steel is 5000m/s, i.e, velocity of solids in metal (solids) is approximately about fifteen times as the velocity of sound in air.

The velocity of sound decreases in this order: solids, liquids and air (gases).

Note: The velocity of sound in air increases by 0.6m/s for every 1oC rise in temperature. To learn more, click here

WEEK 9

RESONANCE

Vibrations in Strings

Fundamental Mode (First Harmonic)

Fundamental Mode – when a string is plucked, it will vibrate in one segment with two nodes at either end.

This is the lowest possible mode of vibration

In a guitar string, for example, it will vibrate between the fret and the tuning key. The bridge transfers the vibration to the “box” (or sound box) through the saddle.

At the fundamental frequency (f0) we have 1 loop and 2 nodes.

Note: # of nodes = # of loops +1. To learn more, click here

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