Explanation

The commutator is a crucial component in a DC motor that reverses the direction of current through the coil every half-cycle.

It is a mechanical switch that rotates with the armature.

It makes contact with the brushes, switching the current flow to the coil as the armature rotates.

Explanation

• When a light ray enters from a denser medium to a rarer medium, it bends away from the normal (a line perpendicular to the surface).

Key Points:

• Denser to rarer: Away from normal
• Rarer to denser: Toward normal

Explanation

In a concave mirror, the image size depends on the position of the object.

As the object moves closer to the mirror, the image size increases, and as it moves away, the image size decreases.

Explanation

A filament is a thin wire, typically made of tungsten, that is heated to produce a continuous flow of electrons.

When an electric current is passed through the filament, it heats up and releases electrons, creating a steady stream of electrons.

This principle is used in various devices such as vacuum tubes, cathode ray tubes (CRTs), and electron microscopes.

Explanation

Electronics comprises the:

• Physics: Study of electrons, semiconductors, and electronic behavior.
• Engineering: Design, development, and testing of electronic systems and devices.
• Technology: Application of electronic principles to create devices, circuits, and systems.

Explanation

The human eye acts like a Camera, capturing light and focusing it onto the retina to form an image.

The eye's lens, aperture, and retina work together to create a visual representation of the world, similar to a camera's mechanism.

Explanation

Telescopes are designed to collect and magnify light from distant objects, such as stars, planets, and galaxies.

They are ideal for viewing faint or dim objects in the night sky, as they can gather more light than the human eye alone.

Explanation

• Dispersion is the optical phenomenon where white light is split into its constituent colors, also known as a spectrum.
• This occurs when light passes through a medium with a refractive index that varies with wavelength, such as a prism.

The process of dispersion involves two stages:

1. Refraction (bending of light)
2. Separation of colors (splitting into distinct colors)

The seven distinct colors that make up the visible spectrum, in order, are:

1. Red
2. Orange
3. Yellow
4. Green
5. Blue
6. Indigo
7. Violet

Explanation

Nuclear fusion is a process where two or more light nuclei (atomic nuclei with a small number of protons and neutrons) combine to form a single, heavier nucleus.

This process releases energy, as the resulting nucleus has a higher binding energy than the original nuclei.

Explanation

Gamma-rays have the highest penetrating power, making them suitable for treating tumors that are deep inside the body.

Gamma-rays are high-energy electromagnetic waves with frequencies higher than X-rays, and they can travel several centimeters into tissue before being absorbed.