Explanation

Formula of parallel plate capacitor:

C = ε₀ x A / d

Where:

C = capacitance = 1 F

ε₀ = permittivity of free space = 8.85 x 10⁻¹² F/m

A = area of plates = ?

d = distance between plates = 1 mm = 0.001 m = 10⁻³ m

We need A:

A = C x d / ε₀

Put values:

A = 1 x 10⁻³ / 8.85 x 10⁻¹²

A = 10⁻³ / 8.85 x 10⁻¹²

A = (1 / 8.85) x 10⁹

A = 0.1129 x 10⁹

A = 1.129 x 10⁸

A ≈ 1.13 x 10⁸ m²

Last verified on 03-11-2026

Explanation

Kinetic Energy = 1/2 x m x v^2

m of electron = 9.1 x 10^-31 kg

v = 10^6 m/s

KE = 0.5 x 9.1 x 10^-31 x (10^6)^2

KE = 0.5 x 9.1 x 10^-31 x 10^12

KE = 4.55 x 10^-19 J

Convert J to eV:

1 eV = 1.6 x 10^-19 J

Energy in eV = 4.55 x 10^-19 / 1.6 x 10^-19

Energy = 2.84 eV

Last verified on 03-11-2026

Explanation

First Law: Delta U = Q + W

Where W = work done ON the system

Delta U = -300 J (decreases)

W = +120 J (work done ON the system)

-300 = Q + 120

Q = -300 - 120

Q = -420 J

Negative sign means 420 J heat is released from the system / heat is transferred out of the system.

Last verified on 03-11-2026

Explanation

• Solid-state detectors detect ionizing radiation by producing electrical signals when radiation interacts with semiconductor material.
• Wilson cloud chambers make the tracks of charged particles visible, helping identify their paths and behaviour.
• Geiger tubes detect ionizing radiation by producing electrical pulses, but they do not directly measure the mass or charge of a particle.

Last verified on 03-11-2026

Explanation

• Cobalt-60 is a radioactive isotope that emits high-energy gamma rays.
• These gamma rays are used in radiotherapy to destroy cancer cells by damaging their DNA.
• Cobalt-60 has been widely used in external-beam cancer treatment, although modern radiotherapy also uses linear accelerators.

Last verified on 03-11-2026