1) A lens with one plane surface and other convex is called___ lens
2) The image formed by a concave lens is____, ____ and______.
3) A ray of light coming parallel to the principal Axis, passes through the ___after refraction in a convex lens.
4) when an object is between D and 2F in a convex lens, the image will form___2F on the other side of the lens.
5) A reading lens is a ____lens.
6) When the medium on both sides of a lens is the ___ both the focal lengths of the lens are equal.
7) The image formed by convex lens is____, ____ and___ when an object is beyond 2F.
8) A____ lens diverges the parallel rays of light coming from a point.
9) The magnification of the image of an object lying at 2F is_____.
10) The image of an object positioned at the focus is formed at _____.
11) A point in a lens at which a ray of lights suffers no refraction is called ______.
B) State whether TRUE or FALSE, Also correct the false statements:
1) A concave lens if kept at a proper distance from an object can form its real image.
2) if the rays of light from a point object actually meet at a point after refraction, the image is virtual.
3) A Ray of light incident parallel to the principal axis of a lens passes undeviated after refraction.
4) A ray of light incident at optical centre of a lens emerges parallel to the principal axis after refraction.
5) A convex lens produces a virtual, inverted and magnified image of an object lies at infinity.
C) DEFINE:
1) Lens
2) Principal axis
3) optical centre
4) First principal focus for a convex lens.
5) First principal focus for a concave lens.
6) Second principal focus for a concave lens.
7) Second principal focus for a convex lens.
8) focal length
9) first focal length
10) second focal length
11) magnification
12) dioptre
D) Short Questions:
1) What are the different kinds of lenses
2) Give any two characteristics of the image produced by concave lens.
3) Is it possible to converge the rays by a concave lens ?
4) which of the two is diverging lens: convex or concave ?
5) State whether a concave lens has a Virtual Focus or real focus.
6) give any two characteristics of the image produced by a convex lens.
7) A lens forms an upright and diminished image of an object irrespective of its position. What kind of lens is this ?
8) A lens forms an inverted image of an object. What kind of lens is this ?
9) Where should an object be placed so that a real and inverted image of the same size as object is obtained using a convex lens ?
10) For what position of an object a real and diminished image is formed by a convex lens ?
11) A convex lens forms the image of an object equal to the size of the object. Where is the object placed in front of the lens ?
12) Name a lens which always forms an erect and virtual image.
13) What will be the nature of the image, real or virtual, if a lens forms an inverted image of an object ?
14) which lens is used for projecting the images on the screen
15) Where should an object to be placed in order to use a convex lens as a magnifying glass ?
16) How is the power of lens related to what kind of lens related to its focal length?
17) What kind of lens can form an:
a) erect diminished image.
b) inverted diminished image.
c) inverted magnified image ?
d) erect magnified image.
18) if the image formed by a lens is always diminished and erect, what is the nature of the lens ?
19) Which type of lens has a:
a) negative power
b) positive power
20) which of the two has a greater power: a lens of short focal length or a lens of large focal length?
21) State the nature of a lens having a power of - 10D.
22) What type of a lens can be used as a magnifying glass ?
23) State three characteristics of the image of an extended source, formed by a concave lens?
24) which physical quantity does the unit dioptre represent.
25) State two applications each of
a) a convex lens
b) a concave lens
26) what do you understand by the term 'power of lens' ? Express the formula for power of lens when focal length is in
a) metres
b) centimetres
E) Diagrammatic questions
1) What are the three convenient rays which are drawn to construct the ray diagram of a lens ?
2) Discuss the formation and characteristics of the image formed by a convex lens when the object is:
a) between the optical centre and the focus
b) at the focus
c) between F and 2F
d) at 2F
e) beyond 2F
f) at infinity
F) Multiple Choice Questions:
1) The point through which a ray of light passes without suffer deviation is called.
i) pole ii) focus iii) centre of curvature iv) optical Centre
2) A convex lens is:
i) thick at the centre and thin at the periphery.
ii) thin at the centre and thick at the periphery.
iii) thick at the centre with one surface as plane.
iv) thin at the centre with one plane surface.
3) Parallel light rays entering a convex lens always converge at:
i) the focal plane
ii) the principle focus
iii) a point on the principle axis.
iv) the centre of the curvature.
4) A Ray of light directed towards the optical Centre:
i) passes through the focus.
ii) becomes parallel to the principal Axis after refraction.
iii) passes undeviated
iv) is reflected back.
5) a concave lens forms the image of an object which is:
i) virtual, inverted and diminished
ii) virtual, upright and diminished
iii) virtual, inverted and enlarge
iv) virtual, upright and enlarged.
6) the magnification for a concave lens is always:
i) less than one
ii) equal to one
iii) more than one
iv) nothing can be said
7) a magnified and erect image is obtained when an object is placed in front of a convex lens. The distance of the object from the lens will be :
i) greater than three focal lengths.
ii) equal to two focal lengths.
iii) between one and two focal lengths.
iv) less than one focal length.
8) An object is placed at 5cm distance from a convex lens of focal length 10cm. the image formed will be:
i) real and inverted
ii) real and enlarged
iii) virtual and diminished
iv) virtual and enlarged
9) an object is placed 50cm from a convex lens of a focal length 30cm. The image formed will be:
i) inverted and of the same size as the object.
ii) inverted and diminished
iii) inverted and magnified
iv) erect and diminished
10) A lens used as a magnifying glass:
i) is a concave lens
ii) produce a virtual image
iii) is placed with the object nearer the lens than the principal focus.
A (a) alone
B (c) alone
C (a) and (b) only
D (b) and (c) only
E (a), (b) and (c)
11) A body is placed at a distance 2f from a convex lens of focal length f. The image is formed:
i) at Infinity ii) at 2f distance iii) between f and 2f distance iv) less than f distance
12) An object is placed at a distance of more than 40cm from a convex lens a focal length 20cm. The image is formed:
i) at a distance less than 20cm
ii) at 20cn distance
iii) between 20cm and 40cm distance
iv) more than 40cm distance
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