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We are learning about:
Competencies:
Examine the scientific and technical information of waves and their applications to comprehend the applications of waves in communication, medicines and entertainment.
Scope:
Types of electromagnetic waves based on frequency and wavelength
Objectives:
Describe scientific properties of electromagnetic waves.
Demonstrate understanding of application of electromagnetic waves for communication over long and short distance by organizing ideas.
VIDEO LESSONS
What is wave? Video lesson
links- To explore its properties, applications, and harmful impacts to gather evidence
NOTES:
Wave: A wave is a disturbance in a medium that carries energy without a net movement of particles. It may take the form of elastic deformation, a variation of pressure, electric or magnetic intensity, electric potential, or temperature.
Speed – The speed of an object means how fast an object moves and is usually expressed as the distance travelled per time of travel. The speed of a wave refers to the distance travelled by a given point on the wave (crest) in a given interval of time
Wave Speed Formula
It is the total distance covered by the wave in a given time period. The formula for wave speed is given as,
Wave Speed = Distance Covered/Time taken
Amplitude – Wave is an energy transport phenomenon. Amplitude is the height of the wave, usually measured in meters. It is directly related to the amount of energy carried by a wave.
Wavelength – The distance between identical points in the adjacent cycles of crests of a wave is called a wavelength. It is also measured in meters.
Period – The period of a wave is the time for a particle on a medium to make one complete vibrational cycle. As the period is time, hence is measured in units of time such as seconds or minutes.
Frequency – Frequency of a wave is the number of waves passing a point in a certain time. The unit of frequency is hertz (Hz) which is equal to one wave per second.
The period is the reciprocal of the frequency and vice versa.
Types of Waves:
Transverse Waves
Waves in which the medium moves at right angles to the direction of the wave.
Examples of transverse waves:
Water waves (ripples of gravity waves, not sound through water)
Light waves
S-wave earthquake waves
Stringed instruments
Torsion wave
The high point of a transverse wave is a crest. The low part is a trough.
Longitudinal Wave:
A longitudinal wave has the movement of the particles in the medium in the same dimension as the direction of movement of the wave.
Examples of longitudinal waves:
Sound waves
P-type earthquake waves
Compression wave
Parts of longitudinal waves:
Compression: where the particles are close together.
Rarefaction: where the particles are spread apart.
Electromagnetic waves
These waves are the disturbance that does not need any object medium for propagation and can easily travel through the vacuum. They are produced due to various magnetic and electric fields. The periodic changes that take place in magnetic electric fields and therefore known as Electromagnetic Wave.
Electromagnetic waves are classified according to their frequency f or according to their wavelength (λ=c/f)
Types of Electromagnetic waves
Radio waves:
Frequency: up to 3 ×1010 Hz
Wavelength: greater than 10 mm
Uses:
Communication
Radio waves are generated artificially by transmitters and received by radio receivers, using antennas.
Radio waves are very widely used in modern technology for fixed and mobile radio communication, broadcasting, radar and radio navigation systems, communications satellites, wireless computer networks and many other applications.
Used in hospitals in MRI (magnetic resonance imaging) to detect tumors to see inside joints, cartilage, ligaments and tendons.
Harmfulness: No definite truth exists on the harmfulness of radio waves, but we should be aware that there could be possible ill-effects.
Click HERE to watch the video lesson on Radio waves
Microwaves:
Frequency: about 3×109 Hz to 3×1013 Hz
Wavelength: about 10-2 m to 10-4 m
Uses:
Heating and data transmission
Microwaves are used in point-to-point communication system i.e. communication between two mobile phones or two computers.
Longer microwaves are used in microwave ovens for cooking. The microwaves vibrate the water molecules present in the food producing heat which helps in cooking.
Television and telephone information are transmitted through long distances from ground stations to communication satellites through microwaves.
Microwaves can be used for transmitting information from one place to another as they can penetrate through fog, clouds, smoke, snow, etc.
Mobile phones, bluetooth and Wi-Fi use microwaves
Shorter microwaves are used in remote sensing. Remote sensing means to gather information about a place or weather conditions from a distance.
Microwaves are used in RADAR to control air traffic, forecast weather, detect speed of vehicles, etc.
Harmfulness:
Prolonged exposure to microwave may cause internal heating of body tissues and may lead to cancer. Some
claims also suggest that cell phone microwaves may instigate brain tumours and cancer.
Click HERE to watch the video lesson on Microwaves
Infrared radiation
lie just beyond the red end of visible part of the spectrum.
Frequency: ranges from 3×1013 Hz to 4×1014 Hz
Wavelength: ranges from about 10-4 m to 7.8×10-7 m
Uses:
Infrared radiation is used for night vision and is used in security camera.
Used in remote control and imaging applications
help to keep us warm by producing heating effect. Example: heat that we get from sunlight, fire, heater, etc is infrared radiation
Shorter infrared waves are used in television remote controls.
used in short range communication.
cooking as they produce heating effect.
transmit signals through optical fibres.
used in security systems
taking photographs at night or in mist or fog.
they are used in astronomy.
produce greenhouse effect
Harmfulness:
They may cause cataracts, corneal ulcers and retinal burns. Exposure to IR waves for long duration of time may cause skin burns.
Click HERE to watch the video lesson on Infrared Radiation
Visible light
The visible light region lies in the middle of the electromagnetic spectrum. The visible light consists of seven colours of light i.e. violet, indigo, blue, green, yellow, orange and red. (VIBGYOR)
Frequency: 4×1014 Hz to 8×1014 Hz
Wavelength: 7.8×10-7 m to 3.8×10-7 m
Uses:
Help us see everything around us
used in electric bulbs, tubelights and lasers.
used in photography.
Harmfulness:
Bright light affects visibility or may even damage our eyes. Therefore, we should never look directly into the Sun or other sources of bright light with our naked eyes.
Click HERE to watch video lesson on Visible Light
Ultraviolet radiations
Frequency: about 8 × 1014 Hz to 3×1016 Hz
Wavelength: 7.8×10-7 m to 1.0×10-8 m
Uses:
UV rays are used to detect forged bank notes. Real bank notes don’t turn fluorescent under the UV light.
Useful in the study of galaxies
used in fluorescent lighting
produce vitamin D in our body.
used for sterilising equipment in hospitals and laboratories.
used in hospitals to cure neonatal jaundice in infants and in the treatment of skin disease called psoriasis.
used in forensics. Crime investigators use UV light to detect fingerprints, body fluids, shoe prints, drugs, etc at the crime scenes.
used in burglar alarms, automatic door openers and counters.
used to detect defects in construction and production in factories.
Harmfulness:
UV rays of shorter wavelength that are harmful to us are mostly absorbed by the ozone layer in the atmosphere.
The acute effects of UV rays are sun burns and tanning of the skin.
premature aging of skin, suppression of immune system, damage to the eyes and skin cancer.
harm the eyes
Click HERE to watch video lesson on Ultraviolet Radiation
X-rays
It can penetrate through soft tissues and skin, has high energy, high frequency
Frequency: Soft X-rays have frequency of about 3× 1016 Hz to 1018 Hz. Hard X-rays have same frequency range as the gamma rays.
Wavelength: Soft X-rays have wavelength ranges from 10-8 m to 10-10 m. Hard X-rays have same wavelength as the gamma rays.
Uses:
Medical instruments to view bone structure to locate fractures and diseased organs in the body.
X-rays are used in airport security scanners
to detect cracks or defects in metal objects
High frequency X-rays are used in computed tomography (CT scans) for the detection of tumours and strokes.
Harmfulness:
They can damage cells causing mutations and cell death which may lead to cancer.
Click HERE to watch video lesson on X-rays
Gamma rays
Frequency: greater than 1018 Hz
Wavelength: less than 10-10 m.
Gamma rays occupy the same range of electromagnetic spectrum as hard X-rays. The only difference between gamma rays and hard X-rays is their source. Gamma rays are produced by radioactive nuclei but hard X-rays are produced by accelerating electrons.
Uses:
Nuclear energy
used in sterilising medical equipment as their high energy can kill germs and bacteria.
used in the treatment of cancer. The cancerous cells can be killed by controlled exposure of these cells to the gamma rays.
Harmfulness: very harmful to us as they are the most energetic of all the electromagnetic waves.
have ionising effects
damage the cells causing mutation and cell death ultimately leading to cancer.
People involved in handling these types of rays are provided with lead coated clothes and equipment. Gamma rays and X-rays can not penetrate through lead. Rooms having X-rays and gamma rays equipment are properly designed with safety measures to prevent the exposure to these rays.
Click HERE to watch video lesson on Gamma rays
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