EM Spectrum

Electromagnetic Spectrum

Master Radio Waves, Microwaves, Infrared, Visible Light, Ultraviolet, X-Rays and Gamma Rays with wavelength ranges, frequency ranges, applications, PYQs and memory tricks.

CBSE NEET JEE Main JEE Advanced IB IGCSE A-Level

What is Electromagnetic Spectrum?

The electromagnetic spectrum is the complete range of electromagnetic waves arranged according to increasing frequency or decreasing wavelength.

All electromagnetic waves travel in vacuum with speed c = 3 × 10⁸ m/s.

c = νλ

E = hν

As frequency increases, energy and penetrating power generally increase, while wavelength decreases.

Complete Electromagnetic Spectrum Diagram

Frequency Range Table

Wave Type	Approx Frequency Range	Important Uses
Radio Waves	10³ Hz to 10⁹ Hz	Radio, TV, communication
Microwaves	10⁹ Hz to 10¹² Hz	RADAR, satellite communication, microwave oven
Infrared	10¹² Hz to 4 × 10¹⁴ Hz	Remote control, thermal imaging, night vision
Visible Light	4 × 10¹⁴ Hz to 8 × 10¹⁴ Hz	Human vision, photography
Ultraviolet	8 × 10¹⁴ Hz to 10¹⁷ Hz	Sterilisation, water purification
X-Rays	10¹⁷ Hz to 10¹⁹ Hz	Medical imaging, security scanning
Gamma Rays	Above 10¹⁹ Hz	Cancer treatment, nuclear research

Wavelength Range Table

Wave Type	Approx Wavelength Range	Exam Point
Radio Waves	> 0.3 m	Longest wavelength
Microwaves	10^-3 m to 0.3 m	Used in RADAR
Infrared	7 × 10^-7 m to 10^-3 m	Heat radiation
Visible	400 nm to 700 nm	VIBGYOR
Ultraviolet	10 nm to 400 nm	Can cause fluorescence
X-Rays	0.01 nm to 10 nm	High penetration
Gamma Rays	< 0.01 nm	Shortest wavelength

Visible Spectrum: VIBGYOR

Violet has shorter wavelength and higher frequency. Red has longer wavelength and lower frequency.

Memory Tricks

Order: Radio → Micro → Infrared → Visible → UV → X-Ray → Gamma

Wavelength: Radio is longest, Gamma is shortest.

Energy: Gamma has maximum energy.

Visible: VIBGYOR from lower wavelength to higher wavelength is reversed in frequency order.

Important MCQs

Q1. Which EM wave has the longest wavelength?

Answer: Radio waves. They have the lowest frequency and longest wavelength.

Q2. Which EM wave has maximum penetrating power?

Answer: Gamma rays, because they have very high frequency and energy.

Q3. Which waves are used in RADAR?

Answer: Microwaves.

Q4. Which part of spectrum is detected by human eye?

Answer: Visible light.

Q5. Which EM waves are used in medical imaging?

Answer: X-rays.

Quick Revision Sheet

c = νλ

E = hν

ν ∝ Energy

λ ∝ 1/ν

Radio = longest λ

Gamma = highest energy

Need Help in Electromagnetic Spectrum?

If frequency ranges, wavelength ranges, applications, spectrum order, NEET PYQs or JEE Advanced questions are not clear, you can learn directly from Kumar Sir through one-to-one online Physics classes.

Contact: +91-9958461445

Website: https://kumarphysicsclasses.com

Email: kumarsirphysics@gmail.com

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Electromagnetic Spectrum: NEET, JEE, CBSE & PYQ-Style Questions

Practice exam-oriented questions based on wavelength range, frequency range, uses, energy order, penetrating power and applications of electromagnetic spectrum.

NEET Q1. Which EM wave has the highest frequency?

Answer: Gamma rays.
Reason: In electromagnetic spectrum, frequency increases from radio waves to gamma rays.

NEET Q2. Which wave is used in RADAR?

Answer: Microwaves.
Reason: Microwaves have short wavelength and can be used for direction detection and ranging.

NEET Q3. Which radiation is used for sterilisation?

Answer: Ultraviolet rays.
Reason: UV rays can kill bacteria and microorganisms.

JEE Q1. If frequency of an EM wave increases, what happens to wavelength?

Formula: c = νλ
Since c is constant in vacuum, wavelength decreases when frequency increases.

JEE Q2. Arrange radio, infrared, X-rays and gamma rays in increasing energy.

Answer: Radio waves < Infrared < X-rays < Gamma rays.
Reason: Energy E = hν.

CBSE Q1. Write two uses of infrared rays.

Answer:
1. Remote controls
2. Thermal imaging / night vision

CBSE Q2. Why are X-rays used in medical diagnosis?

Answer: X-rays have high penetrating power and can pass through soft tissues but are absorbed by bones.

PYQ-Style Q1. Which part of EM spectrum has wavelength just greater than visible red?

Answer: Infrared rays.

PYQ-Style Q2. Which EM radiation has maximum ionising power?

Answer: Gamma rays.

PYQ-Style Q3. Which EM waves are used in satellite communication?

Answer: Microwaves.

Case Study: Electromagnetic Spectrum in Daily Life

A student studies different applications of electromagnetic waves. He observes that radio waves are used in broadcasting, microwaves are used in satellite communication, infrared rays are used in remote controls, ultraviolet rays are used for sterilisation, X-rays are used for medical imaging and gamma rays are used in cancer treatment. He also learns that all electromagnetic waves travel with the same speed in vacuum, but differ in wavelength, frequency and energy.

Case Q1. Which wave is used in TV and radio broadcasting?

Answer: Radio waves.

Case Q2. Which wave is suitable for satellite communication?

Answer: Microwaves.

Case Q3. Which wave is used in remote controls?

Answer: Infrared rays.

Case Q4. Which wave is used for detecting bone fractures?

Answer: X-rays.

Case Q5. Which wave has maximum energy among the given waves?

Answer: Gamma rays.
Reason: Energy of EM wave is E = hν, so higher frequency means higher energy.

Extra MCQs for Practice

1. The correct order of increasing frequency is:

Answer: Radio waves → Microwaves → Infrared → Visible → Ultraviolet → X-rays → Gamma rays

2. Which EM wave has the longest wavelength?

Answer: Radio waves.

3. Which EM wave is used in cancer therapy?

Answer: Gamma rays.

4. Which EM wave is responsible for tanning of skin?

Answer: Ultraviolet rays.

5. Which relation connects speed, frequency and wavelength?

Answer: c = νλ