(a) Explain with the help of a diagram, why the concave lens is also called a perging lens.(b) Define the principal focus of a concave lens.
(a) A concave lens is also called a diverging lens because it diverges or spreads the parallel rays of light passing through it.
Think of a flashlight or torch, in which the light from the small bulb passes through the lens and spreads out into a bigger beam on the other side. Look at the diagram given below.
(b) The principal focus $(F)$ of a concave lens is a point on its principal axis from which all the light rays, originally parallel to the principal axis, appear to diverge after passing through the lens.
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- (a) Explain with the help of a diagram, why the convex lens is also called a converging lens.(b) Define principal axis, principal focus and focal length of a convex lens.
- (a) With the help of a labelled diagram, explain how a concave lens perges a beam of parallel light rays. Mark the principal axis, optical centre, principal focus and focal length of the concave lens on the diagram.(b) State whether concave lens has a real focus or a virtual focus.(c) List some things that concave lens and concave mirror have in common.
- What is a lens? Distinguish between a convex lens and concave lens. Which of the two is a converging lens : convex lens of concave lens?
- (a) With the help of a labelled diagram explain how a convex lens converges a beam of parallel light rays. Mark the principal axis, optical centre, principal focus and focal length of the convex lens on the diagram.(b) State whether convex lens has a real focus or a virtual focus.(c) List some things that convex lens and concave mirror have in common.
- Define the principal focus of a concave mirror.
- You are provided with a concave mirror, a convex mirror, a concave lens and a convex lens. To obtain an enlarged image of an object you can use either$(a)$. concave mirror or convex mirror.$(b)$. concave mirror or convex lens.$(c)$. concave mirror or concave lens.$(d)$. concave lens or convex lens.
- What is a Concave Lens?
- Which type of lens is : (a) a converging lens, and which is (b) a perging lens? Explain your answer with diagrams.
- With the help of a diagram, explain why the image of an object viewed through a concave lens appears smaller and closer than the object.
- A convex lens is said to have a real focus and a concave lens a Virtual Focus.Why?
- You are provided with a convex mirror, a concave mirror, a convex lens and a concave lens. You can get an inverted image from$(a)$. both concave lens and convex lens.$(b)$. both concave mirror and convex mirror.$(c)$. both concave mirror and convex lens.$(d)$. both convex mirror and concave lens.
- The magnification produced by a spherical mirror and a spherical lens is + 0.8.(a) The mirror and lens are both convex (b) The mirror and lens are both concave(c) The mirror is concave but the lens is convex (d) The mirror is convex but the lens is concave
- The magnification produced by a spherical lens and a spherical mirror is + 2.0.(a) The lens and mirror are both concave (b) The lens and mirror are both convex(c) The lens is convex but the mirror is concave (d) The lens is concave but the mirror is convex
- A ray of light is going towards the focus of a concave lens. draw a ray diagram to show the path of this ray of light after refraction through the lens.
- Concave Lens
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