Class 10 Physics — Important Questions with Answers

7 concept-first Class 10 Physics questions across 4 chapters — each with a clear model answer, the why behind it, and a memory trick to make it stick. NCERT-aligned and free. Build the base now, and your board exams, NEET and JEE feel a whole lot easier later.

7 questions•4 chapters•Concept-first•NCERT-aligned•For boards, NEET & JEE

Light - Reflection and Refraction (3)Electricity (2)Magnetic Effects of Electric Current (1)The Human Eye and the Colourful World (1)

Light - Reflection and Refraction3 questions

PhysicsRefraction of lighteasy

Why does a ray of light bend when it passes from air into glass?

Reveal answer▾

What it is

Light bends (refracts) when its speed changes on moving between media of different densities.

Answer

Light bends because its speed changes when it moves from one medium to another. Glass is optically denser than air, so light slows down on entering glass and bends towards the normal. This bending of light due to a change in speed is called refraction.

n = speed in vacuum / speed in medium = c/v

•Speed of light changes between media
•Denser medium -> bends towards the normal
•Governed by refractive index n = c/v

Why learn this

It's why lenses, spectacles, cameras and your own eye can focus - the basis of all optics.

💡 Memory trick

Enter a denser medium -> slow down -> bend TOWARDS the normal (like a car hitting mud).

PhysicsMirror formulamedium

State the mirror formula and the sign convention used for a concave mirror.

Reveal answer▾

What it is

The mirror formula links focal length, object distance and image distance for a curved mirror.

Answer

The mirror formula relates focal length f, image distance v and object distance u as 1/f = 1/v + 1/u. By the New Cartesian sign convention, distances are measured from the pole; distances measured against the incident light (to the left) are negative, so for a concave mirror f and u are negative, and a real image distance v is also negative.

1/f = 1/v + 1/u ; m = -v/u

•1/f = 1/v + 1/u
•Distances measured from the pole (P)
•Concave mirror focal length is negative
•Magnification m = -v/u = h'/h

Why learn this

It's how we design car mirrors, telescopes, torches and a dentist's mirror.

💡 Memory trick

1/f = 1/v + 1/u. In New Cartesian signs, left-of-mirror distances are negative.

PhysicsPower of a lensmedium

A convex lens has a focal length of 25 cm. Find its power.

Reveal answer▾

What it is

The power of a lens tells how strongly it bends light; it is the reciprocal of its focal length in metres.

Object at 24 cm → image at 17.1 cm · diminished, inverted, real (m = -0.71)

Convex lens (f = 10 cm) — slide to move the object across 2F and F

Answer

Power P = 1 / f, where f is the focal length in metres. Here f = 25 cm = 0.25 m, so P = 1 / 0.25 = +4 dioptres (D). The power is positive because it is a convex (converging) lens.

P = 1 / f (dioptre), f in metres

•P = 1 / f (f in metres)
•f = 0.25 m
•P = +4 D (positive for a convex lens)

Why learn this

It's how opticians prescribe your spectacles - the number on the prescription is the power.

💡 Memory trick

Power = 1 / focal length (in metres). Shorter focal length = stronger (higher power) lens.

Electricity2 questions

PhysicsOhm's laweasy

State Ohm's law and define electrical resistance.

Reveal answer▾

What it is

For a conductor at steady temperature, voltage = current x resistance (V = IR).

Answer

Ohm's law states that, at constant temperature, the current I through a conductor is directly proportional to the potential difference V across it, so V = IR. Resistance R is the property of a conductor that opposes the flow of current; it is the ratio of potential difference to current, R = V/I, measured in ohm.

V = IR ; R = V/I

•V is proportional to I at constant temperature
•V = IR
•R = V/I, unit ohm
•Resistance opposes current flow

Why learn this

It's the single most-used rule in all electrical and electronics engineering.

💡 Memory trick

V = IR - the 'VIR' triangle: cover the one you want to find.

PhysicsPower and heating effectmedium

A current of 2 A flows through a 5 ohm resistor. Find the potential difference across it and the power dissipated.

Reveal answer▾

What it is

Electric power is the rate of using electrical energy: P = VI (also I^2 R or V^2 / R).

Answer

Using Ohm's law, V = IR = 2 x 5 = 10 V. Power dissipated P = VI = 10 x 2 = 20 W (equivalently P = I^2 R = 4 x 5 = 20 W).

V = IR ; P = VI = I^2 R = V^2 / R

•V = IR = 10 V
•P = VI = 20 W
•Check: P = I^2 R = 20 W

Why learn this

It's what your electricity bill charges for and why a heater draws far more than a phone charger.

💡 Memory trick

P = VI. If you know current and resistance, use P = I^2 R ('I-squared-R heating').

Magnetic Effects of Electric Current1 question

PhysicsField around a conductoreasy

State the right-hand thumb rule for the magnetic field around a straight current-carrying wire.

Reveal answer▾

What it is

A current in a straight wire creates circular magnetic field lines around it.

Answer

If you hold the straight conductor in your right hand with the thumb pointing in the direction of the current, the curled fingers show the direction of the concentric circular magnetic field lines around the wire.

•Thumb -> direction of current
•Curled fingers -> direction of field
•Field lines are concentric circles around the wire

Why learn this

It's the principle behind electromagnets, electric motors, bells and MRI machines.

💡 Memory trick

Right hand: thumb = current, curled fingers = the circular magnetic field.

The Human Eye and the Colourful World1 question

PhysicsScattering of lightmedium

Why does the clear sky appear blue?

Reveal answer▾

What it is

The sky is blue because tiny air molecules scatter blue light much more than red.

Answer

Sunlight is scattered by the tiny molecules of air in the atmosphere. Blue light has a shorter wavelength and is scattered much more strongly than red light. As this scattered blue light reaches our eyes from all directions, the clear sky appears blue. At sunset the light travels a longer path, most of the blue is scattered away, and the remaining red light makes the sky look reddish.

•Air molecules scatter sunlight
•Blue (shorter wavelength) scatters most
•Scattered blue reaches our eyes -> blue sky
•Sunset: blue scattered away, red remains

Why learn this

The same scattering explains red sunsets and why danger signals are red (least scattered).

💡 Memory trick

Blue scatters most (short wavelength), so the sky looks blue; at sunset the long red light survives.

Start early. Stay ahead.

A few Class 10 Physics questions a day and the concepts become second nature. Explore every subject for Class 10 in the interactive Foundation bank, or ask the AI tutor any doubt the moment it shows up.

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