Jasmine Grover Content Strategy Manager
Content Strategy Manager
Electromagnetic Spectrum is the range of frequencies of electromagnetic radiation and respective wavelengths and photon energies. Maxwell predicted existence of different types of electromagnetic waves. Visible light waves are the only ones that can be seen by us. Electromagnetic Spectrum can also be defined as the distribution of electromagnetic waves in order, according to their wavelength and frequency.
| Table of Content |
Key Terms: Current, Ampere, Wave, Maxwell law’s, Magnetic field lines, Electromagnetic Spectrum, Wavelength, Frequency
Electromagnetic Spectrum
[Click Here for Sample Questions]
Generally, in a vacuum, the EM waves tend to travel at speeds that are similar to those of light, but they travel at a wide range of wavelengths and frequencies. The range of these wavelengths and frequencies that covers frequencies ranging from below 1 Hz to above 1025 Hz is what is known as the Electromagnetic Spectrum.
The EM spectrum can further be divided into gamma-rays, visible light, infrared rays, etc.
Electromagnetic Spectrum
| Frequently Asked Questions Ques. What is the highest frequency color? (1 Mark) Ans. The colour with the highest frequency and highest energy is violet. Ques. What are the main parts of the electromagnetic spectrum? (2 Marks) Ans. In order from highest to lowest energy, sections of the electromagnetic spectrum are named: gamma rays, X-rays, ultraviolet radiation, visible light, infrared radiation, and radio waves. Ques. Give reasons behind the naming of Electromagnetic Spectrum. (2 Marks) Ans. Electromagnetic spectrum is the name given to collection of all electromagnetic radiation in the universe. It is an energy that pervades the cosmos in the form of electric and magnetic waves, allowing for the transfer of energy and information. |
Also check:
| Related Concepts | ||
|---|---|---|
| Electromagnetic Waves MCQ | Impedance of free space | Scintillation Counter |
| Physical Significance of Electric Field | Unit of Wavelength | Total Internal Reflection |
Waves in the EM Spectrum
[Click Here for Previous Year Questions]
The waves in the electromagnetic spectrum can be classified as -
-
Radio Waves -
- The frequency range of radio waves ranges from 500 kHz to about 1000 MHz.
- They are produced by the accelerated motion of charges in conducting wires.
- Radios pick up the waves that are transmitted by the radio stations.
- Radio waves are also used for mobile/TV communication.
-
Microwaves -
- Microwaves are essentially short-wavelength radio waves.
- The frequency range of microwave waves is between 3*1011 – 1013 Hz.
- These radiations are used for aircraft navigation radar systems, speed testing (via speed guns) and, most significantly, in the kitchen appliance, the microwave.
- Astronomers also make use of these radiations to understand the structure of nearby stars and galaxies.
-
Infrared -
- The frequency range of infrared waves is 1013 – 1014 Hz.
- They are generally produced by hot bodies and molecules.
- These waves are used in Earth satellites, night vision goggles, remote switches for household appliances, etc.
- Infrared waves play an essential role in maintaining the earth’s warmth/average temperature.
- These are also known as “Heat Waves”.
-
Visible Rays -
- The frequency range of visible rays is 4 – 7.5*1014 Hz.
- These rays are the most familiar as they can be detected by human eyes.
- The rays emitted or reflected from light sources like bulbs, stars, etc. are known as visible rays.
-
Ultraviolet -
- The frequency range of ultraviolet rays is 10-15 – 10-17 Hz.
- These rays are emitted by the sun and are harmful to humans when exposed for longer durations. The ozone layer absorbs these harmful rays, thus protecting us.
- Water purifiers sometimes also make use of UV lamps in order to kill the germs in the water.
- UV radiations can have medical applications by being focused into very narrow beams for high-precision surgeries such as LASIK.
-
X-rays -
- The frequency range of X-rays is 1017 – 1020 Hz.
- X-rays are most commonly used for diagnostic purposes in the medical world.
- They are used to take images of our teeth or bones and are used in cancer treatments and are used in airport scanners.
- Overexposure to X-ray radiation can cause damage to living tissues.
-
Gamma Rays -
- The frequency range of gamma rays is 1020 – 1024 Hz.
- These are high-frequency radiations produced in nuclear reactions and are also emitted by radioactive nuclei.
- Medically, they are also used to destroy cancer cells.
| Solved Examples Example: List the properties of electromagnetic waves. Solution: Properties of Electromagnetic Waves are:
Example: Arrange these electromagnetic waves in increasing order of their frequencies (i.e., begin with the lowest frequency):
Solution: Electromagnetic waves in increasing order of their frequency: Radio waves \(\rightarrow\) Micro waves \(\rightarrow\) Infrared waves \(\rightarrow\) Visible light \(\rightarrow\) Ultraviolet radiations \(\rightarrow\) X rays \(\rightarrow\) γ rays |
Significance of Electromagnetic Spectrum
[Click Here for Sample Questions]
Maxwell predicted the existence of infinite frequencies of electromagnetic waves, all traveling with the speed of light, through his equations. This is the first indication of the existence of the entire electromagnetic spectrum.
The electromagnetic waves are produced in different ways. The difference in bands reflects different characteristics based on how they are produced, their interaction with matter, and their practical applications.
The main significance of the Electromagnetic Spectrum is that it can be used to classify electromagnetic waves and arrange them according to their different frequencies or wavelengths.
Practical Applications of EM Waves
[Click Here for Previous Year Questions]
- Radio waves and microwaves are used for the purpose of wireless radio, television, and mobile communication.
- Visible light rays help us to see everyday objects around us, as well as discerning all colors
- Infrared rays have military applications by deploying observational satellites. As well as maintaining the earth’s temperature.
- Ultraviolet rays aid in ionizing atoms for chemical reactions, aiding in water purification.
- X-rays are primarily used as a diagnostic tool to detect skeletal ailments and treat certain cancers.
- Gamma rays have primarily nuclear applications and are used to destroy cancer cells.
In short, the classification of the Electromagnetic Spectrum can be summarized as below -
| Type of Radiation | Frequency Range in Hz | Wavelength Range | Uses |
|---|---|---|---|
| Gamma-rays | 1020 – 1024 | < 10-12 m | Sterilize medical equipment, Medical Treatment, Treatment of cancer without surgery |
| X-rays | 1017 – 1020 | 1 nm – 1 pm | Treat tumors, Detect brain fractures or sprains |
| Ultraviolet | 1015 – 1017 | 400 nm – 1 nm | Disinfection, Sterilization without the use of chemicals |
| Visible | 4 – 7.5*1014 | 750 nm – 400 nm | For performing scientific experiments and in LEDs |
| Infrared | 1013 – 1014 | 25 μm – 2.5 μm | Study human body heat patterns, used in infrared cameras |
| Microwaves | 3*1011 – 1013 | 1 mm – 25 μm | Used for cooking in microwaves |
| Radio waves | < 3*1011 | > 1 mm | Used in the operation of radio through catching frequencies |
Things to Remember
- Maxwell predicted the existence of various types of electromagnetic waves, out of which the visible light waves were the only ones that could be seen by us.
- The range and classification of all these types of electromagnetic radiations based on their frequency are known as the Electromagnetic Spectrum.
- The Electromagnetic Spectrum can also be defined as the distribution of electromagnetic waves in order, according to their wavelength and frequency.
- Radio waves are also used for mobile/TV communication. The frequency range of infrared waves is 1013 – 1014 Hz.
- The main significance of the Electromagnetic Spectrum is that it can be used to classify electromagnetic waves and arrange them according to their different frequencies or wavelengths.
- X-rays are primarily used as a diagnostic tool to detect skeletal ailments and treat certain cancers. Gamma rays have primarily nuclear applications and are used to destroy cancer cells.
Electromagnetic Waves Solved Problems
Also check:
| Chapter Related Links | ||
|---|---|---|
| Gamma Radiation | Faraday's Law | Huygens Principle |
| Displacement Current | Electrical Insulators | Radio Waves |
| Wave Speed | Transverse and Longitudinal Waves | Electric Charges and Fields |
Sample Questions
Ques. What is the use of microwaves? (1 Mark)
Ans. Microwave radiations are chiefly used for cooking in the microwave. The microwave uses radiation by directly transferring energy to the water molecules present in food items. Astronomers also make use of these radiations to understand the structure of nearby stars and galaxies.
Ques. Which type of waves are also known as 'heatwaves? (2 Marks)
Ans. Infrared waves are referred to as ‘heatwaves because they are produced by hot bodies or molecules. The absorption of infrared waves by water molecules present in substances leads to an increase in thermal motion. Thus, not only does the substance heat up but so do their surroundings.
Ques. Why are visible rays important? (2 Marks)
Ans. The fact that we are blind to most EM rays, makes the presence of visible rays even more precious. The entire world is oriented around these visible rays for humans. The gift of sight allows us to function effectively leading to the development of the human race. The light that is reflected or emitted from objects allows for intellectual perception, making visible rays extremely important for all living creatures.
Ques. In the order of increasing frequency, the electromagnetic spectrum may be arranged as: (2 Marks)
Ans. The electromagnetic spectrum is a continuum of all electromagnetic waves arranged as per frequency and wavelength. As shown in the image the order of increasing frequency is: Radio waves, Visible light, X-rays and Gamma rays.
Ques. A magnetron in a microwave oven emits electromagnetic waves (em waves) with frequency f = 2450 MHz. What magnetic field strength is required for electrons to move in circular paths with this frequency? (5 Marks)
Ans. Frequency of the electromagnetic waves given is f = 2450 MHz
The corresponding angular frequency is
ω= 2πf = 2 x 3.14 x 2450 x 106
= 15,386 x 106 Hz
= 1.54 × 1010 s-1
The magnetic field B = meω / |q|
Mass of the electron, me = 9.22 x 10-31 kg
Charge of the electron
q =−1 . 60 ×10−19 C ⇒ |q| = 1.60 ×10−19 C
\(B = \frac{(9.22 \times 10^{-31})(1.54 \times 10^{10})}{(1.60 \times 10^{19})} = 8.87425 \times 10^{-2}T\)
B = 0.0887 T
This magnetic field can be easily produced with a permanent magnet. So, electromagnetic waves of frequency 2450 MHz can be used for heating and cooking food because they are strongly absorbed by water molecules.
Ques. Which part of the electromagnetic spectrum does the wavelength 10−10 m correspond to? (1 Mark)
Ans. X-rays of the electromagnetic spectrum correspond to the wavelength 10−10m.
Ques. What maximum light wavelength will excite an electron in the valence band of diamond to the conduction band? The energy gap is 5.50eV. (5 Marks)
Ans. Since the electron jumps from the conduction band to the valence band, the energy of the photon equals the energy gap between those two bands.
The photon energy is given by hf=hc/λ, where f is the frequency of the electromagnetic wave and λ is its wavelength. Thus, Eg=hc/λ and
\(\lambda = hc/Eg = (6.63 × 10^-34J.s)(2.998 × 10^8 m/s)/(5.5eV)(1.60 × 10^-19J/eV) = 2.26 × 10^-7m = 226nm\)
Photons from other transitions have greater energy, so their waves have shorter wavelengths.
Previous Year Questions
- Which of the following electromagnetic radiations have the longest wavelength… [NEET 1989]
- A 100Ω resistance and a capacitor of 100Ω reactance are connected in series… [NEET 2016]
- The electric field part of an electromagnetic wave in a medium is represented by… [NEET 2009]
- If λv,λx,λm represent the wavelengths of visible light… [NEET 2005]
- A parallel plate capacitor of capacitance 20μF is being charged by a voltage… [NEET 2019]
- A radiation of energy 'E ' falls normally on a perfectly reflecting surface… [NEET 2015]
- An electromagnetic wave of frequency υ = 3.0 MHz passes from vacuum into… [NEET 2013]
- Biological importance of ozone layer is… [NEET 2001]
- For a transparent medium relative permeability and permittivity… [NEET 2019]
- If ε0 and μ0 are the electric permittivity and magnetic permeability in a free… [NEET 1997]
- Light with an energy flux of 25×104Wm−2 falls on a perfectly reflecting surface… [NEET 2014]
- The electric field associated with an e.m. wave in vacuum is given by… [NEET 2012]
- The ratio of contributions made by the electric field and magnetic field… [NEET 2020]
- The velocity of electromagnetic wave is parallel to… [NEET 2002]
- Wavelength of light of frequency 100 Hz… [NEET 1999]
- What is the cause of ''Green house effect''… [NEET 2002]
- The electric and magnetic field of an electromagnetic wave are… [NEET 1994]
- In which of the following, emission of electrons does not take place… [NEET 1990]
- The condition under which a microwave oven heats up a food item containing… [NEET 2013]
- Which of the following statement is false for the properties of electromagnetic… [NEET 2010]
For Latest Updates on Upcoming Board Exams, Click Here: https://t.me/class_10_12_board_updates
Check-Out:
Comments