Explanation

When two circles touch each other externally, they have a single point of contact.

The distance between their centers (C1C2) is equal to the sum of their radii (r1 + r2).

Explanation

When an object is placed at the principal focus (F) of a convex lens, the rays emerge parallel after refraction.

Parallel rays appear to meet at infinity, so the image is formed at infinity (very far away).

Explanation

• Venus, often called the "Evening Star" or "Morning Star," appears in the western sky after sunset.
• Venus is the brightest planet.
• It has an atmosphere but no moons.
• It's identical in size, chemistry and gravity.
• It has volcanoes, mountains and sand.
• It's also called Sister Planet of the Earth.

Explanation

Change in momentum = 20 − 5 = 15 kg·m/s

Time = 3 s → Force = 15 / 3 = 5 N

Explanation

Restoring force 𝐹 = −𝑘𝑥 depends on displacement 𝑥.

At the mid position, x = 0, so restoring force is minimum (zero).

Explanation

The energy density (u) in a capacitor is given by:

u = ½ε₀E²

Where:

- ε₀ is the permittivity of free space

- E is the electric field intensity between the plates

This shows that the energy density is proportional to the square of the electric field intensity (E²).

Explanation

The kinetic energy (KE) of an electron in the nth orbit is given by:

KE = 1/2mv²n

Where m is the mass of the electron and vn is its velocity in the nth orbit.

Explanation

Magnetic induction 𝐵 represents the amount of magnetic flux passing per unit area — hence called magnetic flux density.

It is measured in tesla (T) in the SI system.

Explanation

Tungsten has the highest melting point among these metals.

It is used in high-temperature applications due to its ability to withstand extreme heat.

Explanation

A spectrometer is an instrument used to measure the properties of light over a specific portion of the electromagnetic spectrum, especially to analyze line spectra produced by atoms or molecules.

It helps identify elements or compounds by detecting their unique emission or absorption lines in the spectrum.