Electromagnetic Waves

Environmental Effects - Ozone, Greenhouse and Safety

What protects the Earth from most of the sun's ultraviolet radiation?

**Greenhouse effect** IR absorbed by CO₂, H₂O, CH₄, warming Earth, excessive greenhouse due to fossil fuel burning raises temperature, EM waves role: Sun visible reaches surface, Earth emits IR trapped, altering energy balance, safety concern for climate change. The document states that the ozone layer absorbs most of the ultraviolet radiation from the sun at an altitude of about 40-50 km . Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Ozone layer, illustrating EM wave transverse nature and Maxwell's displacement current concept.

Ref: NCERT > Physics Book > Electromagnetic Waves > Environmental Effects - Ozone, Greenhouse and Safety

View Details

Applications of EM Waves in Communication and Medicine

Which of Maxwell's equations relates the electric field to the rate of change of magnetic flux?

**Microwaves in ovens** cause water molecules to rotate at 2.45 GHz, friction heats food, penetration depth few cm, efficient heating, also radar uses reflection of microwaves from objects, Doppler shift measures speed, medical diathermy uses microwaves for tissue heating. Faraday's Law in Maxwell's equations states oint E · d l = -(d Φ_B/d t) , describing the induction of an electric field by a changing magnetic field. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Faraday's Law, illustrating EM wave transverse nature and Maxwell's displacement current concept.

Ref: NCERT > Physics Book > Electromagnetic Waves > Applications of EM Waves in Communication and Medicine

View Details

Applications of EM Waves in Communication and Medicine

Which type of electromagnetic waves are produced by special vacuum tubes like klystrons and magnetrons?

**Radio waves** effective for long-distance communication because low frequency waves diffract around Earth curvature and reflect from ionosphere, enabling beyond line-of-sight, used in AM (≈10⁶ Hz) ground wave, short wave sky wave. Microwaves used for satellite due to high frequency penetrates ionosphere and directional beam. The document mentions that microwaves are produced by special vacuum tubes such as klystrons and magnetrons. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Microwaves, illustrating EM wave transverse nature and Maxwell's displacement current concept.

Ref: NCERT > Physics Book > Electromagnetic Waves > Applications of EM Waves in Communication and Medicine

View Details

Applications of EM Waves in Communication and Medicine

Which frequency range includes TV waves according to the document?

**X-rays and gamma rays in medicine** X-rays imaging because bone absorbs more than tissue, contrast, CT scan uses multiple X-ray projections, gamma knife uses focused gamma rays to destroy tumor with minimal surrounding damage, illustrating high-energy EM wave medical use. The document states that TV waves range from 54 MHz to 890 MHz . Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields 54 MHz to 890 MHz, illustrating EM wave transverse nature and Maxwell's displacement current concept.

Ref: NCERT > Physics Book > Electromagnetic Waves > Applications of EM Waves in Communication and Medicine

View Details

Applications of EM Waves in Communication and Medicine

An electromagnetic wave has a wave number \( k = 1 \, \text{rad/m} \). What is its wavelength in vacuum?

**Microwaves in ovens** cause water molecules to rotate at 2.45 GHz, friction heats food, penetration depth few cm, efficient heating, also radar uses reflection of microwaves from objects, Doppler shift measures speed, medical diathermy uses microwaves for tissue heating. The wave number k = (2 π/λ) . Given k = 1 rad/m , we have λ = (2 π/k) = (2 π/1) ≈ 6.28 m . Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields 6.28 m, illustrating EM wave transverse nature and Maxwell's displacement current concept.

Ref: NCERT > Physics Book > Electromagnetic Waves > Applications of EM Waves in Communication and Medicine

View Details

Applications of EM Waves in Communication and Medicine

What is the typical wavelength range of gamma rays as per the electromagnetic spectrum?

**Radio waves** effective for long-distance communication because low frequency waves diffract around Earth curvature and reflect from ionosphere, enabling beyond line-of-sight, used in AM (≈10⁶ Hz) ground wave, short wave sky wave. Microwaves used for satellite due to high frequency penetrates ionosphere and directional beam. The document states that gamma rays have wavelengths from about 10⁻¹⁰ m to less than 10⁻¹⁴ m . Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields 10⁻¹⁰ m to 10⁻¹⁴ m, illustrating EM wave transverse nature and Maxwell's displacement current concept.

Ref: NCERT > Physics Book > Electromagnetic Waves > Applications of EM Waves in Communication and Medicine

View Details

Applications of EM Waves in Communication and Medicine

In the electromagnetic spectrum, what distinguishes gamma rays as particularly penetrating?

**X-rays and gamma rays in medicine** X-rays imaging because bone absorbs more than tissue, contrast, CT scan uses multiple X-ray projections, gamma knife uses focused gamma rays to destroy tumor with minimal surrounding damage, illustrating high-energy EM wave medical use. Gamma rays have extremely short wavelengths (high frequencies), resulting in very high energy, which allows them to penetrate deeply through materials, including dense substances. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields High energy, illustrating EM wave transverse nature and Maxwell's displacement current concept.

Ref: NCERT > Physics Book > Electromagnetic Waves > Applications of EM Waves in Communication and Medicine

View Details

Applications of EM Waves in Communication and Medicine

A capacitor in a circuit has a conduction current of \( 1.8 \, \text{A} \) in the wires. What is the displacement curren

**Microwaves in ovens** cause water molecules to rotate at 2.45 GHz, friction heats food, penetration depth few cm, efficient heating, also radar uses reflection of microwaves from objects, Doppler shift measures speed, medical diathermy uses microwaves for tissue heating. The document states that in a charging capacitor, the displacement current between the plates equals the conduction current in the wires, so i_d = 1.8 A . Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields 1.8 A, illustrating EM wave transverse nature and Maxwell's displacement current concept.

Ref: NCERT > Physics Book > Electromagnetic Waves > Applications of EM Waves in Communication and Medicine

View Details

Applications of EM Waves in Communication and Medicine

Which type of electromagnetic waves are emitted by hot bodies and molecules?

**Radio waves** effective for long-distance communication because low frequency waves diffract around Earth curvature and reflect from ionosphere, enabling beyond line-of-sight, used in AM (≈10⁶ Hz) ground wave, short wave sky wave. Microwaves used for satellite due to high frequency penetrates ionosphere and directional beam. The document states that infrared waves are produced by hot bodies and molecules, often referred to as heat waves. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Infrared waves, illustrating EM wave transverse nature and Maxwell's displacement current concept.

Ref: NCERT > Physics Book > Electromagnetic Waves > Applications of EM Waves in Communication and Medicine

View Details

Applications of EM Waves in Communication and Medicine

What type of charges cannot produce electromagnetic waves?

**Microwaves in ovens** cause water molecules to rotate at 2.45 GHz, friction heats food, penetration depth few cm, efficient heating, also radar uses reflection of microwaves from objects, Doppler shift measures speed, medical diathermy uses microwaves for tissue heating. The document states that neither stationary charges nor charges in uniform motion (steady currents) can produce electromagnetic waves; only accelerated charges can. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Stationary charges, illustrating EM wave transverse nature and Maxwell's displacement current concept.

Ref: NCERT > Physics Book > Electromagnetic Waves > Applications of EM Waves in Communication and Medicine

View Details

Applications of EM Waves in Communication and Medicine

What physical quantity is the same for all electromagnetic waves in vacuum?

**Radio waves** effective for long-distance communication because low frequency waves diffract around Earth curvature and reflect from ionosphere, enabling beyond line-of-sight, used in AM (≈10⁶ Hz) ground wave, short wave sky wave. Microwaves used for satellite due to high frequency penetrates ionosphere and directional beam. All electromagnetic waves in vacuum travel at the same speed, c = 3 × 10⁸ m/s , regardless of their frequency or wavelength. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Speed, illustrating EM wave transverse nature and Maxwell's displacement current concept.

Ref: NCERT > Physics Book > Electromagnetic Waves > Applications of EM Waves in Communication and Medicine

View Details

Applications of EM Waves in Communication and Medicine

What is the frequency range of the AM radio band?

**X-rays and gamma rays in medicine** X-rays imaging because bone absorbs more than tissue, contrast, CT scan uses multiple X-ray projections, gamma knife uses focused gamma rays to destroy tumor with minimal surrounding damage, illustrating high-energy EM wave medical use. The document states that the AM (amplitude modulated) band ranges from 530 kHz to 1710 kHz . Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields 530 kHz to 1710 kHz, illustrating EM wave transverse nature and Maxwell's displacement current concept.

Ref: NCERT > Physics Book > Electromagnetic Waves > Applications of EM Waves in Communication and Medicine

View Details