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Light – Reflection and Refraction

Which of the following statements is true?
(a) A convex lens has 4 dioptre power having a focal length 0.25 m
(b) A convex lens has –4 dioptre power having a focal length 0.25 m
(c) A concave lens has 4 dioptre power having a focal length 0.25 m
(d) A concave lens has –4 dioptre power having a focal length 0.25 m

Light – Reflection and Refraction

A beam of light is incident through the holes on side A and emerges out of the holes on the other face of the box as shown in the Figure . Which of the following could be inside the box?

(a) Concave lens
(b) Rectangular glass slab
(c) Prism
(d) Convex lens

Light – Reflection and Refraction

Beams of light are incident through the holes A and B and emerge out of box through the holes C and D respectively as shown in the Figure. Which of the following could be inside the box?

(a) A rectangular glass slab
(b) A convex lens
(c) A concave lens
(d) A prism

Light – Reflection and Refraction

A light ray enters from medium A to medium B as shown in Figure. The refractive index of medium B relative to A will be

(a) greater than unity
(b) less than unity
(c) equal to unity
(d) zero

Light – Reflection and Refraction

Under which of the following conditions a concave mirror can form an image larger than the actual object?
(a) When the object is kept at a distance equal to its radius of curvature
(b) When object is kept at a distance less than its focal length
(c) When object is placed between the focus and centre of curvature
(d) When object is kept at a distance greater than its radius of curvature

Light – Reflection and Refraction

A 10 mm long awl pin is placed vertically in front of a concave mirror. A 5 mm long image of the awl pin is formed at 30 cm in
front of the mirror. The focal length of this mirror is
(a) – 30 cm (b) – 20 cm
(c) – 40 cm (d) – 60 cm

Light – Reflection and Refraction

Which of the following can make a parallel beam of light when light from a point source is incident on it?
(a) Concave mirror as well as convex lens
(b) Convex mirror as well as concave lens
(c) Two plane mirrors placed at 90° to each other
(d) Concave mirror as well as concave lens

Heredity and Evolution

Give reasons for the appearance of new combinations of characters in the F₂ progeny.

Heredity and Evolution

Give the basic features of the mechanism of inheritance.

Heredity and Evolution

Evolution has exhibited a greater stability of molecular structure when compared with morphological structures. Comment on the statement and justify your opinion.