Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
COMEDK2012PhysicsRay Optics

A convex lens of focal length F is placed in contact with a concave lens of focal length F . The equivalent focal length of the combination is

Options

  1. Ainfinity
  2. BF/2
  3. C2 F
  4. Dzero

Correct answer

A. infinity

Step-by-step solution

Given, f₁=F and f₂=-F The equivalent focal length of combination of two lenses is 1 f = 1 f₁ + 1 f₂ = 1 F + 1 -F =0 or f= 1 0 = (infinity)

Practice Ray Optics on Quantrex Academy →

More from Ray Optics

The critical angle for a typical glass air interface is 42^ . If a ray of light falls normally on one of the faces of the prism of angle 45^ . The emergent ray will: 2026The distance between the objective and eye piece of astronomical telescope in normal adjustment is 27 cm and its magnifying power is 8. What is the focal length of the objective le 2026The ratio of the angle of deviation produced by a thin prism, when it is placed in air to the angle of deviation produced when it is immersed in water of refractive index 4 3 is: 2026An object placed 40 cm in front of a thin convex lens is moved to 60 cm from the lens. If the focal length of the lens is 30 cm the ratio of magnification of the image at the initi 2026A glass slab of 16 cm thickness has its bottom surface silvered. An air bubble is located inside the glass slab at a distance of 8 cm from the top surface. The refractive index of 2026If a clear liquid has a refractive index of 1.45 and a transparent solid has a refractive index of 2.9, then for total internal reflection to occur at the interface between the two 2026An object is placed at an unknown distance from a convex objective lens of focal length 8 cm. The objective lens forms a real image which acts as an object for a convex eyepiece of 2026An object is placed 25 cm in front of a fully silvered concave mirror of focal length 15 cm. A plane mirror is placed 35 cm behind the concave mirror on the side opposite to the ob 2026 Full Ray Optics list All COMEDK PYQs