Electromagnetic Radiation Questions

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Very Short Answers Questions [1 Mark Questions]

Ques. As per quantum mechanics, electromagnetic radiations behave like discrete particles known as

1. Photons
2. Atom
3. Electron
4. Molecules

Ans. The correct answer is a. Photons

Explanation: According to quantum theory, photons constantly travel at the universal speed of light. Electromagnetic radiation is defined as the flow of photons.

Ques. The unified theory of electromagnetism was explained by

1. Albert Einstein
2. Kelper
3. James Clerk Maxwell
4. Faraday

Ans. The correct answer is c. James Clerk Maxwell

Explanation: In 1873, James Clerk Maxwell described relationships between the mobility of charged particles in electric and magnetic fields and the behavior of electric and magnetic fields in his unified theory of electromagnetism.

Ques. What is meant by the atmospheric window?

Ans. The atmospheric window is the wavelength of electromagnetic radiation that can travel through the Earth's atmosphere.

Ques. Photons have _____ rest mass.

1. Unit
2. Zero
3. Less
4. More

Ans. The correct answer is b. Zero

Explanation: Photons are chargeless and massless particles that move at the speed of light. As a result, the rest mass of a photon is assumed to be zero.

Ques. A short wavelength indicates that the frequency will be

1. Lesser
2. Zero
3. Higher
4. None of the above

Ans. The correct answer is c. Higher

Explanation: A shorter wavelength indicates a higher frequency since one cycle may pass in a shorter amount of time.

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Short Answers Questions [2 Marks Questions]

Ques. What is electromagnetic radiation?

Ans. Electromagnetic radiation is a type of energy produced by the movement of electrically charged particles or the oscillation of electric and magnetic fields. Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays are all examples of electromagnetic waves.

Ques. What is the electromagnetic spectrum?

Ans. The electromagnetic spectrum includes all electromagnetic radiation, from high-energy gamma rays to low-energy radio waves, with visible light which includes only a small portion in the center. The electromagnetic spectrum is essential for understanding and utilizing various types of electromagnetic energy.

Ques. What is the main source of electromagnetic radiation heat on Earth?

Ans. The sun is the primary source of electromagnetic radiation for our planet. The sun's energy travels to the Earth's surface through space and the Earth's atmosphere. Some of this energy becomes heat energy and it heats the earth's surface and atmosphere.

Ques. What is radiation?

Ans. The emission or transmission of energy in the form of waves or particles across space or a material medium is referred to as radiation.

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Long Answers Questions [3 Marks Questions]

Ques. What is the electromagnetic radiation theory?

Ans. Electromagnetic radiation theory is the theory that represents the evolution of electromagnetic waves. When an electric current is carried through a body or surface, electromagnetic radiation is present, according to the hypothesis. The proposed theory was as follows:

• The electric charges between them, which represent the force of attraction or repulsion, are inversely proportional to the square of the distance between them.
• Magnetic poles exist in pairs and, like electric charges, attract and repel one another.
• The direction of an electric current's magnetic field is determined by the direction of the electric current.
• Moving electric fields generate magnetic fields, and vice versa.

Ques. How electromagnetic waves are produced?

Ans. Electromagnetic waves are composed of electric and magnetic field waves produced by moving charges. 

• All electromagnetic waves begin with a charged particle. 
• This charged particle generates an electric field (which can exert force on other charged particles in the vicinity). 
• When a charged particle accelerates as part of an oscillatory motion, it causes ripples, or oscillations, in its electric field as well as a magnetic field (as predicted by Maxwell's equations).
• Once a charged particle is in motion, the electric and magnetic fields it generates are self-perpetuating time-dependent changes in one field (electric or magnetic) that produce the other. 
• In an electromagnetic wave, both the electric and magnetic fields will vary over time, with one influencing the other to change.
• Electromagnetic waves (photons) are created whenever a charged particle's velocity changes.

Ques. How does electromagnetic energy interact with matter?

Ans. Depending on the wavelength of the radiation, electromagnetic waves can interact with matter in a number of ways.

• Radio waves and microwaves may pass through a variety of materials, including paper and wood. As a result, they may be used for communication as well as remote sensing.
• Molecules may absorb infrared light, causing them to vibrate. As a result, infrared radiation can be used to heat and cook.
• Matter may reflect, refract, and absorb visible light. This is how we see objects and colors.
• Ultraviolet light has the ability to ionize atoms, taking electrons from them. Because of this, UV light may be used to sterilize medical equipment as well as cause sunburns.

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Very Long Answers Questions [5 Marks Questions]

Ques. What are the properties of electromagnetic waves?

Ans. The following are the properties of electromagnetic waves

• They are transverse in nature
• They propagate in the form of changing electric and magnetic fields in such a way that these two fields are at right angles to each other and at right angles to the wave's propagation direction.
• In a vacuum, electromagnetic waves have a constant velocity. The waves have a speed of 3 x 10⁸ m/s.
• They are non-mechanical waves and do not require a medium for their propagation.
• They follow the formula c = λf. Here, f is the frequency in Hertz and λ is the wavelength in meters. The product of wavelength and frequency equals a constant c, which is equal to 3 x 108 m/s, the speed of light.
• The oscillating electric and magnetic fields are in phase. The velocity of the wave is equal to the ratio of the amplitudes of the electric and magnetic fields.

Ques. What are the different types of electromagnetic radiation?

Ans. The different types of electromagnetic radiation are

• Gamma-rays: In the electromagnetic spectrum, gamma rays have the highest frequency and photon energy. They are connected with nuclear processes and high-energy particle interactions and have extremely short wavelengths.
• X-rays: X-rays have somewhat lower frequencies and photon energy than gamma rays. Because of their capacity to penetrate materials and show interior structures, they are frequently employed in medical imaging, security screening, and industrial applications.
• Ultraviolet (UV) rays: Ultraviolet rays have higher photon energy and frequency than visible light. They are released by the Sun and serve an important role in biological processes such as vitamin D production as well as initiating chemical reactions in the atmosphere.
• Visible light: Visible light is the part of the electromagnetic spectrum that can be seen with the naked eye. Visible light is required for eyesight. It possesses a variety of frequencies and photon energies that enable humans to detect different colors.
• Infrared (IR) rays: Infrared rays have lesser photon energy and frequency than visible light. They are associated with heat radiation and are often utilized in applications such as night vision, remote sensing, and infrared spectroscopy.
• Radio waves: Radio waves have the lowest photon energy and frequencies in the electromagnetic spectrum. They are used in communication systems, broadcasting systems, and radar systems. Different parts of the radio wave spectrum are assigned to different purposes, such as AM and FM radio, television, and mobile communication.
• Microwaves: Microwaves have a slightly higher photon energy and frequency than radio waves. Microwave ovens, satellite communication, and wireless technology all use them.

Ques. What are the characteristics of electromagnetic radiation?

Ans. The following are the characteristics of electromagnetic radiation

• Wavelength: The distance between successive crests or troughs of a wave is represented by its wavelength (λ). It is the length of one complete oscillation cycle. 
• Amplitude: The maximum displacement of a wave from its equilibrium position is referred to as its amplitude. It denotes the distance from the wave's center to the crest or trough.
• Frequency: The number of wave cycles that occur every second, measured in Hertz (Hz) or cycles per second, is referred to as frequency. It specifies how many times a wave oscillates in a certain time period.
• Period: The period (T) of a wave is the amount of time it takes to complete one full cycle or traverse one wavelength. It is given by the reciprocal of frequency i.e. T = 1/f. The time period of a wave tells us about the time characteristics of a wave.
• Velocity: Velocity is defined in electromagnetic radiation as the product of wavelength and frequency, which is given by Velocity = λf. In a vacuum, the velocity of electromagnetic waves is equal to the speed of light, which is about 186,282 miles per second or 2.99 x 10⁸ meters per second (m/s).

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