Electromagnetic waves are the waves which carry energy by the variations of electric and magnetic fields. Infrared radiation, visible light, and ultraviolet radiation are examples of Electromagnetic waves.
Visible light is defined as the form electromagnetic radiation or wavelength that are visible to human eye. Visible lights are produced by flames and discharge tubes. Wavelength of visible light ranges from 4\(\times\) 10-7m to 8 \(\times\) 10-7m. Long wavelength visible light is red light with 8 \(\times\) and short wavelength visible light is violet with 4 \(\times\) 10-7m. The frequency range of visible light is between 400 to 790 THz. Visible light is used in communication.
It is a form of electromagnet radiation which is invisible to human eye. The wavelength of infrared radiation ranges from 10-5m to 5 \(\times\) 10-3m. We cannot see infrared radiation but we can feel due to its heat. The frequency range of infrared radiation is between 430THz to 300GHz. Infrared is used in night vision where the is not enough light. It is also used in tracking, heating, and communication. Sun also produced infrared radiation. We cannot see them as they are invisible but we feel hot or warm due the infrared radiation of the sun when we stay in sunlight.
Radio waves is a type of electromagnetic radiation. It is widely used in communication, in television, cell phones, radios, etc. It is used in the transmission of data in coded form. In the form of radar, it is used also for sending out signals and picking up their reflections from objects in their path. It has the longest wavelength among all the electromagnetic spectrum. The wavelength of radio waves ranges from 10-4m to 5 \(\times\)104m. It is produced by electrical oscillations and is detected by radio receivers or similar tuned circuits. The frequency of radio waves ranges from 300GHz to 3Hz.
|Its average wavelength and frequency are 10-8 and 1015 Hz respectively.||Its average wavelength and frequency are 10-10 and 1018 Hz respectively.|
|It is obtained from sun, tube light etc.||It is obtained by x-ray machine.|
|Ultraviolet rays||Infrared rays|
|The frequency is high.||The frequency is low.|
|They have more energy.||They have less energy.|
|They are harmful.||They are not harmful.|
The process of splitting up of white light into seven visible colors is known as dispersion of light.
The dispersion of light can be seen through prism, in rainbow, soap bubbles, etc.
The speed of all colors in vacuum is same. When the white light enters a denser medium the speed as well as wavelength of each color decreases and they separate with each other. On leaving the medium, its speed increases than its original value. The red light has the maximum speed whereas the violet light has the minimum speed within the denser medium.
So, red light deviate the least and violet light deviates the most and other colors lie between red and violet. It is the cause of dispersion.
The prism has triangular shape. When a beam of light enters the face AB of prism, it gets refracted towards BC and strikes the face AC. When the rays enter to air from glass, they further separate with each other. Hence, a prism disperses a white light.
The two opposite surfaces of glass slab are parallel with each other. The surface AB refracts a beam of light and produces a spectrum of seven colors. When these colors strikes the surface CD, then all the color get mixed up and white light emerged out to the air again. This is why light is not dispersed on passing through a glass slab.
Two advantages of the ultraviolet rays are as follows:
|Mechanical wave||Electromagnetic wave|
|Mechanical waves are the disturbance that require a material medium to propogate. Eg: sound waves||Electromagnetic waves are the waves in which the variation of electric and magnetic field takes place during their propagation.Eg: light waves|
|They cannot transmit without medium||They can transmit without medium.|
The electromagnetic waves are classified according to their wavelength or frequency. The range of wavelength or frequency of electromagnetic waves is called electromagnetic spectrum.
The main properties of electromagnet are as follows:
|They have shorter wavelength||They have longer wavelength.|
|They have high penetrating power.||They have low penetrating power.|
|They are harmful to our body.||They are not harmful.|
The light waves with wide range of wavelengths (10-5m to 5 x 104m) and lie on the spectrum just beyond the infrared region is called radio waves.
The radio waves are not harmful to our body because they have longer wavelength and very low frequency and have less penetrating power.
The uses of x-rays and y-rays are as follows: