NEET 2016 Phase 2 · PhysicsPrevious Year Question
Two identical glass (µ_g = 3/2) equiconvex lenses of focal length f each are kept in contact. The space between the two lenses is filled with water (µ_w = 4/3). The focal length of the combination is
Answer: (D) 3f/4. Answer: (D) 3f/4 Solution: For one equiconvex glass lens, both radii are equal in magnitude R, so 1/f = (µ_g − 1)(2/R) = (3/2 − 1)(2/R) = 1/R Hence 1/R = 1/f.
- A.f/3
- B.f
- C.4f/3
- D.3f/4✓
Correct Answer
(D) 3f/4
Solution & Explanation
Answer: (D) 3f/4 Solution: For one equiconvex glass lens, both radii are equal in magnitude R, so 1/f = (µ_g − 1)(2/R) = (3/2 − 1)(2/R) = 1/R Hence 1/R = 1/f. The water between the two lenses acts as an equiconcave lens (radii −R and +R as seen by water): 1/f_w = (µ_w − 1)(−2/R) = (4/3 − 1)(−2/R) = −(1/3)(2/R) = −2/(3R) = −2/(3f) The combination is three thin lenses in contact: 1/F = 1/f + 1/f_w + 1/f = 1/R + 1/R − 2/(3R) 1/F = 2/f − 2/(3f) = (6 − 2)/(3f) = 4/(3f) Therefore F = 3f/4.
🎯
43,000+ questions in हिंदी & English · one-tap toggle
Open →📚Practice all NEET Physics PYQs chapter-wise →💡Don't get it? Learn the Ray Optics And Optical Instruments concepts →Practice NEET 2016 Phase 2 Physics — free, with instant solutions
43,000+ NEET questions solved step-by-step, chapter-wise, in the MedicNEET app.
More NEET PYQ solutions
PhysAn electric dipole with dipole moment 5 × 10⁻⁶ C·m is aligned with the direction of a uniform electric field of magnitude 4 × 10⁵ N/C. The dipole is then rotated through an angle of 60° with respect to the electric field. The change in the potential energy of the dipole is:PhysThe plates of a parallel plate capacitor are separated by d. Two slabs of different dielectric constant K1 and K2 with thickness 3d/8 and d/2 respectively are inserted in the capacitor. Due to this, the capacitance becomes two times larger than when there is nothing between the plates. If K1/K2 = 1.25, the value of K1 is:PhysA ball of mass 0.5 kg is dropped from a height of 40 m. It hits the ground and rebounds to a height of 10 m. The impulse imparted to the ball during its collision with the ground is (g = 9.8 m/s²):PhysA 2 A current is flowing through two different small circular copper coils having radii ratio 1 : 2. The ratio of their respective magnetic moments will bePhysAn electron (mass 9 × 10⁻³¹ kg and charge 1.6 × 10⁻¹⁹ C) moving with speed c/100 (c = speed of light) is injected into a magnetic field B of magnitude 9 × 10⁻⁴ T perpendicular to its direction of motion. We wish to apply a uniform electric field E together with the magnetic field so that the electron does not deflect from its path. Then (speed of light c = 3 × 10⁸ m s⁻¹)PhysA container has two chambers of volumes V₁ = 2 litres and V₂ = 3 litres separated by a partition made of a thermal insulator. The chambers contain n₁ = 5 and n₂ = 4 moles of ideal gas at pressures p₁ = 1 atm and p₂ = 2 atm, respectively. When the partition is removed, the mixture attains an equilibrium pressure of:PhysTwo gases A and B are filled at the same pressure in separate cylinders with movable pistons of radius r_A and r_B, respectively. On supplying an equal amount of heat to both systems reversibly under constant pressure, the pistons of gas A and gas B are displaced by 16 cm and 9 cm, respectively. If the change in their internal energy is the same, then the ratio r_A/r_B is equal to:PhysAn oxygen cylinder of volume 30 litre has 18.20 moles of oxygen. After some oxygen is withdrawn from the cylinder, its pressure drops to 11 atmospheric pressure at temperature 27 °C. The mass of the oxygen withdrawn from the cylinder is nearly equal to: [Given R = 100/12 J mol⁻¹ K⁻¹, molecular mass of O₂ = 32, 1 atm = 1.01 × 10⁵ N m⁻²]