IMAGE OF A PLANE MIRROR

• It is a virtual image
• Laterally Inverted
• Upright
• The same distance from the source.

REAL IMAGE	VIRTUAL IMAGE
1. Image can be obtained on a screen.	1. Image cannot be obtained on a screen
2. The rays actually meet where the image is formed.	2. The rays happen to meet where the image is formed.
eg Images of the cinema

TYPES OF REFLECTION

REFRACTION

• Bending of light as it travels from one medium to another.
• Light bends because speed of light is different in different medium.
• If the light is travelling from rarer to denser medium then it bends towards the normal. ∠r < ∠i
• If the light is travelling from denser to rarer medium then it bends away from the normal.∠r > ∠i

The pencil appears to be broken as the light is refracted in water.

VISIBLE LIGHT

Visble light is a spectrum of 7 colours VIBGYOR Each colour has its own freqency and wavelength. The visible colour of the object will be the colour that is reflected by the object. Opaque Object Opaque objects does not allow the light to be transmitted but absorb all the light. eg Book, Translucent Object These objects allow some part of the light to be transmitted. eg Plastic Transparent Object They allow the light to be transmitted through them without any absorption eq glass

SOUND WAVES

• They are longitudnal Waves.
• Sound does not travel through a medium.
• Sound requires a medium to travel.
• Sound wave is characterized by compression and rarefaction.
• In sound waves, particles vibrate parallel to the direction of the wave.

The speed of the sound wave is 330m/s. Human hearing range 20 Hz to 20,000 Hz In Echo sounding, high frequency sound waves are sent to determine the depth or find any object. The time taken by the sound to come back is noted for the known speed of sound. S = vt/2

ULTRASOUND

It is the frequency of sound greater than 20,000 Hz. ADVANTAGES

• 1. They are non ionizing and harmless.
• 2. They are partially reflected at the boundaries between different tissues, so they can scan even the soft tissues.

USES 1. Used in prenatal scanning. 2. Used to determine the depth of the sea or the obstacle inside 3. Industrial Imaging . 4. Detecting flaws in metal castings. water.

USES OF ULTRASOUND

ULTRASOUND SCANNER

Transducer sends ultrasound waves. It crosses the body and reflected from the tissues. The Transducer detects the waves reflected from the tissues and the image is diplayed on the screen in the form of scans.

SONAR

• Ultrasound waves are used to measure the depth of the sea or find the obstacle under water.
• In SONAR, ultrasound is sent to determine the depth or find any object.
• The time taken by the sound to come back is noted for the known speed of sound.

STRUCTURE OF THE EARTH

The crust and the upper mantle cracks and forms the tectonic plate. The Tectonic Plates causes Earthquake.

SEISMIC WAVES

• Earthquake takes place when the rocks or the tectonic plates in the Earth’s Crust or the upper Mantle Moves due to forces inside the Earth.
• Seismic Waves are the shock waves which originate when the forces inside the earth moves the rocks or the tecctonic plates. These waves travel through the Earth and also across its surface.
• The Earthquake are detected by Seismometer.
• The focus is the point from where the Earthquake originates.
• Seismology is the study of Seismic Waves.
• The nearest point on the surface of the focus is the epicenter.

SEISMIC WAVES

P-Wave	S-Wave
·        They are longitudinal ·        They are faster than other waves. ·        They can travel through solids and liquids. ·        They can pass through liquid outer core.	·        They are transverse ·        They are slower than other waves ·        They travel through solids only ·        S-waves cannot pass through the liquid outercore.

• Shadow Zones are the place where no P and S waves are detected.
• S shadow zones where no S wave and only P waves are detected.

P and S Wave travel through the Mantle changing directions with depth. P waves refract at the boundary between mantle and outer core. S waves being transfer do not travel through liquid outer core. 1. Liquid Outer core under the Mentle. Shadow zones are detected as P waves refract twice. Once while entering the core from the mantle and leaving the core from the mantle. Since the refraction is further away forming shadow zones it suggests a liquid outer core under the mantle. 2. Solid Inner Core Weak P waves in the shadow zones caused by the refraction of P waves while crossing the boundary between outer core and inner core. Long (L-waves) travel the slowest. They happen only in the Earth’s crust and they cause more violent movements.

ELECTROMAGNETIC SPECTRUM

• It is the spectrum with all the electromagnetic waves arranged in the order of the increasing wavelength or frequency.
• Electromagnetic waves are electric and magnetic disturbances that transfer energy (no matter) from one point to another.
• All the electromagnetic waves travel with the speed of light-3 x10 8m/s
• The frequency and the wavelength can be given by the formuale :- V = Fλ

ELECTROMAGNETIC SPECTRUM MNEMONIC

GAMMA RAYS

SOURCE

Gamma rays are produced when the radiactive substance emit nuclear radiations.

PROPERTIES

• They have the lowest wavelength.
• They have highest frequency.
• They travel with the speed of light.

USES

1. They are uses to disinfect food and surgical equipment. 2. It is used to kill cancer cells. In gamma treatment, the cobalt 60 is used to direct the gamma radiation to the cancer cells and kill it without affecting the surrounding tissue.

DISADVANTAGES

1. Gamma Rays are highly ionizing. 2. Exposure to low dose of Gamma Rays can cause gene mutation, DNA damage and even cancer. 3. Exposure to high dose of Gamma radiation can caused killing of the cell.

X-RAYS

SOURCES

They are produced by stopping high speed electrons. PROPERTIES 1. They are electromagnetic wave which travels with the speed of light. 2. They have wavelength greater than Gamma Rays but smaller than ultraviolet rays. 3. They have lower frequency than Gamma Rays but greater than ultraviolet rays. 4. Their wavelength is about the diameter of the atom.

USES

1. Shorter wavelength X-rays are used in X-ray therapy to kill cancer cells without destroying the healthy cells. 2. Longer wavelength X-rays are used to photograph the internal structure of the body.

DISADVANTAGES

1. X-Rays are highly ionizing 2. Exposure to a low dose of Gamma Rays can cause gene mutation, DNA damage and even cancer. 3. Exposure to a high dose of Gamma radiation can caused killing of the cell.

HOW X-RAYS WORK ?

• X-rays are passed through the body.
• The X-rays passes through the soft tissues but are absorbed by the bones and harder tissues.
• The X-rays that pass through the softer areas reach the detector and appears to be black whereas the rays that are absorbed do not reach the detector and appears light in the image.
• If any organs containing softer tissues needs to be photographed then patient is given a contrasting medium like Barium which becomes a good absorber of X-rays and helps the photography of that organ.
• The detector contains the charged coupled device CCD which converts X-rays to light which then creates electronic signal which are used by the computer to make a digital image.

ULTRA VIOLET RAYS

SOURCE

1. They are produced from the Sun. The Sun is the source of ultraviolet rays.

PROPERTIES

1. They are electromagnetic wave which travels with the speed of light. 2. They have wavelength greater than X-Rays but smaller than Violet light. 3. They have lower frequency than X- Rays but greater than violet light.

USES

They are uses as fluorescent markers or fluorescent lamps which contains the chemical which converts UV Light to Visible Light.

DISADVANTAGES

1. They can cause sunburn and suntan 2. They can also lead to skin cancer. 3. They can also lead to blindness.

VISIBLE LIGHT

SOURCE

1. Sun and lamps emits light 2. It is the only part of the specturm which is visible.

PROPERTIES

1. It is made up of 7 colours 2. VIOLET INDIGO BLUE GREEN YELLOW ORANGE RED 3. When the white light is passed through the prism, it can give the spectrum of colours.

USES

• Light is used in a camera to take the picture.
• Light is also used in Light Microscope
• Light helps to see the object.
• Light waves are also used in communication.

DISADVANTAGES

Too much exposure to visible light can lead to cancer, blindness and skin damage.

INFRA RED WAVES

SOURCE

• All the hot objects like Kettle, Toaster, Radiator emits infrared radiation.

PROPERTIES

1. They are electromagnetic wave which travels with the speed of light. 2. They have wavelength greater than visible light but smaller than Microwaves. 3. They have a lower frequency than visible light but greater than microwaves.

USES

1. They are used in optical fibres for communication. 2. They are used in remote controls. 3. They are used as infrared scanners to detect heat produced by the body and unhealthy tissues 4. Infrared cameras helps to see objects in dark.

DISADVANTAGES

1. They can cause sunburn and suntan 2. They can also lead to skin cancer. 3. They can also lead to blindness.

MICROWAVES

The water in the food absorb microwaves and become heated and heats the food preventing the microwave from heating as it has no water.

SOURCE

• They are emitted as Cosmic Microwave Background Radiation. Sun also emits some microwaves.

PROPERTIES

1. They are electromagnetic wave which travels with the speed of light. 2. They have wavelength greater than infrared light but smaller than Radiowaves. 3. They have a lower frequency than infrared light but greater than radiowaves. 4. They are found between Radiowaves and Infrared Waves.

USES

1. They are used in communication. 2.They are used in satellite TV. 3. They are used in cooking. 4. They are used to carry mobile phone signal.

DISADVANTAGES

1. Exposure to microwaves can heat the body tissues. 2. Exposure to high dose of microwaves can cause eye damage and even cataract.

RADIOWAVES

SOURCE

Radio waves can be generated by natural sources such as lightning or astronomical phenomena; or by artificial sources such as broadcast radio towers, cell phones, satellites and radar.

PROPERTIES

1. They are electromagnetic wave which travels with the speed of light. 2. They have the highest wavelength. 3. They have the lowest frequency.

USES

• They are used in communication to carry TV, radio and mobile signals.
• They are used in wireless connection and bluetooth connection.

DISADVANTAGES

1. Exposure to radiowave can heat the body tissues. 2. Exposure to high dose of radiowaves can cause eye damage and even cataract.

LENSES

They are used to refract the light and forms the image of an objects. They are used in camera.

CONVEX LENS	CONCAVE LENS
1.   It is a converging lens 2. It is thicker at the center than at the edges 3. It has a real focus 4. It converges a parallel beam of light on refraction through it 5. It is used in microscope, magnifying glass 6. Used to correct short sight	1.   It is a diverging lens.         2. It is thinner at the center than at the edges. 3. It has a virtual focus 4. It diverges a parallel beam of light on refraction through it. 5. Used in some telescopes 6. Used to correct long sight.

CONCAVE LENS

mages formed is virtual, upright and smaller than the object.

CONVEX LENS

KEY TERMS

• Waves:- Waves are oscillations or disturbance that transfer energy from one point to another.
• TRANSVERSE WAVES:- In transverse waves, the oscillations move perpendicular to the direction of the wave.
• CRESTS :- It is the height of the wave.
• AMPLITUDE :- It is the maximum displacement of the wave from the mean Position.
• LONGITUDNAL WAVES :- In longitudnal waves, the oscillations move parallel to the direction of the wave.
• FREQUENCY :- It is the number of waves passing each second. It is measured in Hertz (Hz)
• WAVE SPEED:- It is the distance travelled by the wave each second.
• TROUGH :- Trough It is the depth of the wave.
• TIME PERIOD :- The time it takes for one wave to travel.
• WAVELENGTH :- The distance between two consecutive crests or trough.
• REFLECTION :- Reflection is the phenomenon of bouncing off the wave when it hits a medium. eq: Reflection of light wave when it hits a plain Mirror.
• REFRACTION :- 1. Bending of light as it travels from one medium to another.

2. Reflection on a smooth surface. 3. Reflection on a rough surface.

• OPAQUE :- Opaque objects does not allow the light to be transmitted but absorb all the light.
• TRANSLUCENT :- These objects allow some part of the light to be transmitted.
• TRANSPARENT :- They allow the light to be transmitted through them without any absorption.
• ULTRASOUND:- It is the frequency of sound greater than 20,000 Hz.
• EARTHQUAKE:- Earthquake takes place when the rocks or the tectonic plates in the Earth’s Crust or the upper Mantle Moves due to forces inside the Earth.
• SEISMOLOGY:- Seismology is the study of Seismic Waves.
• SEISMIC WAVES:- Seismic Waves are the shock waves which originate when the forces inside the earth moves the rocks or the tecctonic plates. These waves travel through the Earth and also across its surface.
• ELECTROMAGNETIC SPECTRUM:- It is the spectrum with all the electromagnetic waves arranged in the order of the increasing wavelength or frequency.
• FOCUS:- Principle Focus or Focal points where the parallel rays meet or appears to meet.
• LENS:- They are used to refract the light and forms the image of an objects. They are used in camera.
• CONVEX LENS:- 1. It is a converging lens.
• CONCAVE LENS:- 1. It is a diverging lens.
• FOCAL LENGTH:- The distance between the focus and the center of the lens.

Disclaimer:

I have tried my level best to cover the maximum of your specification. But this is not the alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it. References: BBC Bitesize Wikipedia Wikimedia Commons Image Source: Wikipedia Wikimedia Commons Flickr Pixabay