Explanation

Dentists use concave mirrors to illuminate inaccessible places in the tooth.

The concave shape of the mirror allows it to reflect light and images from small, hard-to-reach areas.

Such as the back of the mouth or between teeth.

Explanation

When a wave passes from one medium to another, its frequency remains unchanged.

However, its speed, wavelength, and direction may change.

Explanation

Mass is not a characteristic of a wave.

The characteristics of a wave include:

• Amplitude (the maximum displacement of the wave from its equilibrium position)
• Period (the time taken by the wave to complete one oscillation)
• Velocity (the speed at which the wave travels)
• Wavelength (the distance between two consecutive points on the wave that are in phase)
• Frequency (the number of oscillations per unit time)

Explanation

Very high frequency is the ITU designation for the range of radio frequency electromagnetic waves from 30 to 300 megahertz,

with corresponding wavelengths of ten to one meter.

ND17-7-2023

Explanation

Perhaps the most familiar example of resonance in everyday life is swinging on a playground swing.

The first push or pump sets the swing in motion.

Each subsequent push or pump is delivered at just the right time to increase the amplitude of swing.

Explanation

 According to Gauss's Law, the net electric flux through a closed surface depends on the net charge enclosed.

If equal and opposite charges are present inside the surface, their total is zero, so the net electric flux is also zero.

Explanation

The energy of a photon is calculated using the formula E = hf, where:

• h = Planck’s constant
• f = frequency of the photon

This shows that photon energy is directly proportional to its frequency.

Explanation

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