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

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

Linear thermal expansion of a solid depends on:

• Increase in temperature
• Original length
• Properties of the material

Explanation

The springs in brakes and clutches are used to restore the original position of the components after they have been engaged or disengaged.

For example, in a brake system, the springs return the brake pads to their original position after the brake pedal is released.

Similarly, in a clutch system, the springs return the clutch plate to its original position after the clutch pedal is released.

Explanation

• Zero error is a type of systematic error that occurs when the instrument's zero point is not accurately calibrated, resulting in a consistent error in all measurements.
• Systematic errors are biases that affect the accuracy of a measurement, and zero error is a specific type of systematic error.

Explanation

• CNSA (China National Space Administration) is a government agency of the People's Republic of China.
• It was established in 1993.
• It is responsible for civil space administration and international space cooperation.

Explanation

Progressive waves are waves that transfer energy from one point to another through a medium, such as a solid, liquid, or gas.

They are also known as mechanical waves, and examples include:

• Water waves
• Sound waves
• Seismic waves (earthquakes)