The heat capacity at constant pressure Cp is greater than heat capacity at constant volume Cv for ideal gases because:

The correct answer is A: At constant pressure, some energy goes into work expansion. At constant P: Q = ΔU + PΔV, so more heat is needed to produce same temperature rise. Relation: Cp - Cv = R

An electric dipole with dipole moment p is placed in uniform electric field E at angle θ to the field. The torque on dipole is:

The correct answer is A: τ = pE sinθ. Torque on dipole in uniform field: τ = p × E = pE sinθ, where θ is angle between dipole moment and field

The binding energy per nucleon of ²⁵⁶Fe (Z=26) is 8.8 MeV. The total binding energy of this nucleus is approximately:

The correct answer is A: 2250 MeV. Total binding energy = (Binding energy per nucleon) × (Mass number) = 8.8 × 256 ≈ 2253 MeV ≈ 2250 MeV.

A charged particle with charge q and mass m enters a magnetic field region with velocity v perpendicular to B. The radius of circular motion is given by:

The correct answer is A: r = mv/(qB). From qvB = mv²/r, we get r = mv/(qB). This is the radius of curvature for a charged particle in a perpendicular magnetic field.

An object experiences a net force of 10 N and accelerates at 2 m/s². Its mass is:

The correct answer is B: 5 kg. From F = ma, m = F/a = 10/2 = 5 kg

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JEE Physics
Optics

Physics questions for JEE Main — Mechanics, Electrostatics, Optics, Modern Physics.

31 Q 9 Topics Take Mock Test

Difficulty: All Easy Medium Hard 1–10 of 31

Topics in JEE Physics

All Mechanics 100 Thermodynamics 100 Electrostatics 100 Current Electricity 100 Magnetism 100 Optics 100 Modern Physics 100 Semiconductors 100 Waves 100

Q.1 Easy Optics

The resolving power of a microscope increases when:

A Wavelength of light increases

B Numerical aperture decreases

C Wavelength of light decreases

D Focal length of objective increases

Correct Answer: C. Wavelength of light decreases

EXPLANATION

Resolving power = 1/(minimum resolvable distance) ∝ 1/λ. Shorter wavelength gives better resolution. UV microscopy uses shorter wavelengths.

Test

Q.2 Easy Optics

A lens of power -5 diopters is used to correct vision. This lens is:

A Convex lens for myopia

B Concave lens for myopia

C Convex lens for hypermetropia

D Concave lens for presbyopia

Correct Answer: B. Concave lens for myopia

EXPLANATION

Negative power indicates concave lens (f = -20 cm). Concave lens is used to correct myopia (short-sightedness).

Test

Q.3 Easy Optics

When white light passes through a prism, violet light deviates more than red light because:

A Violet has smaller wavelength

B Violet has larger refractive index

C Violet has higher frequency

D All of the above

Correct Answer: D. All of the above

EXPLANATION

Violet has smaller λ, higher frequency, and the medium has higher n for violet (dispersion). All factors lead to greater deviation.

Test

Q.4 Easy Optics

Critical angle for a medium is 45°. Its refractive index is:

A √2

B 2

C 1/√2

D 0.5

Correct Answer: A. √2

EXPLANATION

sin(critical angle) = 1/n. sin(45°) = 1/√2 = 1/n, therefore n = √2 ≈ 1.414

Test

Q.5 Easy Optics

A concave mirror of focal length 20 cm forms a real, inverted, and magnified image. The object must be placed:

A Between pole and focus

B At the focus

C Between focus and center of curvature

D Beyond center of curvature

Correct Answer: C. Between focus and center of curvature

EXPLANATION

For magnified real image in concave mirror, object distance u must be between f and 2f (between focus and center of curvature), giving magnification m > 1.

Test

Q.6 Easy Optics

Light of wavelength 500 nm in vacuum enters a medium of refractive index 1.5. The wavelength in the medium is:

A 333.3 nm

B 500 nm

C 750 nm

D 250 nm

Correct Answer: A. 333.3 nm

EXPLANATION

Wavelength in medium = λ_vacuum / n = 500/1.5 = 333.3 nm. Frequency remains constant in different media.

Test

Q.7 Easy Optics

A plane mirror is moved towards a stationary object at a speed of 5 m/s. The speed at which the image approaches the object is:

A 5 m/s

B 10 m/s

C 2.5 m/s

D 0 m/s

Correct Answer: B. 10 m/s

EXPLANATION

When mirror moves towards object at speed v, the image also moves towards object at speed v. Therefore, relative speed = v + v = 2v = 10 m/s

Test

Q.8 Easy Optics

The refractive index of a material is found to be 1.5. The speed of light in this material is:

A 1.5 × 10⁸ m/s

B 2.0 × 10⁸ m/s

C 3.0 × 10⁸ m/s

D 2.5 × 10⁸ m/s

Correct Answer: B. 2.0 × 10⁸ m/s

EXPLANATION

n = c/v. 1.5 = (3 × 10⁸)/v. v = (3 × 10⁸)/1.5 = 2 × 10⁸ m/s

Test

Q.9 Easy Optics

A lens has power +5 D. A second lens of power -2 D is placed in contact with it. The equivalent focal length of the combination is:

A 0.33 m

B 0.25 m

C -0.33 m

D -0.25 m

Correct Answer: A. 0.33 m

EXPLANATION

Power combination: P = P₁ + P₂ = 5 + (-2) = 3 D. Focal length f = 1/P = 1/3 = 0.33 m

Test

Q.10 Easy Optics

An object is placed 15 cm in front of a concave mirror with focal length 10 cm. The magnification of the image formed is:

A +2

B -2

C +0.5

D -0.5

Correct Answer: B. -2

EXPLANATION

Using mirror formula: 1/f = 1/u + 1/v. 1/10 = 1/15 + 1/v. v = 30 cm. Magnification m = -v/u = -30/15 = -2

Test

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