Light - Reflection and Refraction

The angle of incidence on a plane mirror is 30 degrees. The angle of reflection will be:

1. a90 degrees
2. b60 degrees
3. c30 degrees
4. d0 degrees

An object is placed in front of a plane mirror at a distance of 20 cm. The distance of the image from the object is:

1. a10 cm
2. b20 cm
3. c60 cm
4. d40 cm

The figure shows a concave mirror with its principal axis, pole \(P\), focus \(F\) and centre of curvature \(C\) marked. An object (green up-arrow) is placed at \(C\) with two rays drawn to construct the image. Based on this ray diagram, the image of the object is formed:

1. aBeyond \(C\), real, inverted and magnified
2. bAt \(F\), real, inverted and diminished
3. cAt \(C\), real, inverted and same-sized as the object
4. dAt infinity, real and very large

According to the New Cartesian Sign Convention for spherical mirrors, with the object placed to the left of the mirror, which statement is correct?

1. aAll distances parallel to the principal axis are measured from the centre of curvature
2. bDistances measured to the left of the pole are taken as positive
3. cHeights measured below the principal axis are taken as positive
4. dDistances measured to the right of the pole are taken as positive

An object is placed 30 cm in front of a concave mirror of focal length 20 cm. Using the mirror formula \(\dfrac{1}{f} = \dfrac{1}{v} + \dfrac{1}{u}\) (with \(f = -20\), \(u = -30\)), the image distance \(v\) is:

1. a\(+60\) cm (behind mirror, virtual)
2. b\(-60\) cm (in front of mirror, real)
3. c\(+12\) cm
4. d\(-12\) cm

An object is placed at \(2F_{1}\) in front of a convex lens. The image is formed at:

1. a\(F_{2}\), real, inverted, diminished
2. bInfinity, real, magnified
3. c\(2F_{2}\), real, inverted, same-sized
4. d\(F_{1}\), virtual, erect, magnified

The power of a convex lens of focal length 50 cm is:

1. a\(+0.5\ \text{D}\)
2. b\(+50\ \text{D}\)
3. c\(-2\ \text{D}\)
4. d\(+2\ \text{D}\)

Which mirror is used by dentists to examine teeth, giving a magnified erect image?

1. aConcave mirror with the tooth between pole and focus
2. bConvex mirror at large distance
3. cPlane mirror
4. dConvex mirror with the tooth at the focus

Assertion (A): A convex mirror is used as a rear-view mirror in vehicles.

Reason (R): Convex mirrors form an erect, diminished image of objects behind the vehicle and provide a wider field of view.

1. aBoth A and R are true, and R is the correct explanation for A
2. bBoth A and R are true, but R is NOT the correct explanation for A
3. cA is true, but R is false
4. dA is false, but R is true

Assertion (A): The image formed by a plane mirror is laterally inverted.

Reason (R): The image formed by a plane mirror is at the same distance behind the mirror as the object is in front, with the same size as the object.

1. aBoth A and R are true, and R is the correct explanation for A
2. bBoth A and R are true, but R is NOT the correct explanation for A
3. cA is true, but R is false
4. dA is false, but R is true

Assertion (A): A ray of light bends towards the normal when it enters water from air.

Reason (R): Light slows down on entering an optically denser medium, causing it to bend towards the normal at the interface.

1. aBoth A and R are true, and R is the correct explanation for A
2. bBoth A and R are true, but R is NOT the correct explanation for A
3. cA is true, but R is false
4. dA is false, but R is true

Assertion (A): A lens of shorter focal length has higher power than a lens of longer focal length.

Reason (R): Power of a lens is the reciprocal of its focal length expressed in metres; a shorter focal length means a greater bending of light, hence higher power.

1. aBoth A and R are true, and R is the correct explanation for A
2. bBoth A and R are true, but R is NOT the correct explanation for A
3. cA is true, but R is false
4. dA is false, but R is true

1. I. The angle of incidence equals the angle of reflection on a plane mirror.
2. II. The incident ray, the reflected ray and the normal at the point of incidence all lie in the same plane.

Which of the above is/are correct?

1. aOnly I
2. bOnly II
3. cBoth I and II
4. dNeither I nor II

1. I. A concave mirror always forms a virtual, erect and magnified image, regardless of object position.
2. II. A convex mirror always forms a virtual, erect and diminished image, regardless of object position.
3. III. A plane mirror always forms a virtual, erect and same-size image.

Regarding mirrors, which of the above is/are correct?

1. aI, II and III
2. bOnly III
3. cOnly I and III
4. dOnly II and III

1. I. The refractive index of a medium is the ratio of the speed of light in vacuum to the speed of light in that medium.
2. II. Light travels faster in an optically denser medium than in a rarer medium.
3. III. When light goes from a less dense medium to a more dense medium, it bends towards the normal.

Regarding refractive index, which of the above is/are correct?

1. aOnly II and III
2. bOnly I and III
3. cOnly I and II
4. dI, II and III

1. I. The power of a lens in dioptre is the reciprocal of its focal length expressed in metres.
2. II. Convex lenses have positive power and concave lenses have negative power.
3. III. A lens with a smaller focal length has greater power than a lens with a larger focal length.

Regarding power of a lens, which of the above is/are correct?

1. aOnly I and II
2. bOnly II and III
3. cOnly I and III
4. dI, II and III

Match each optical element with its STANDARD use:

1. a(i)-Q, (ii)-P, (iii)-R, (iv)-S
2. b(i)-P, (ii)-R, (iii)-Q, (iv)-S
3. c(i)-Q, (ii)-R, (iii)-S, (iv)-P
4. d(i)-S, (ii)-Q, (iii)-R, (iv)-P

Match the position of object in front of a CONVEX LENS with the image formed:

1. a(i)-P, (ii)-R, (iii)-Q, (iv)-S
2. b(i)-Q, (ii)-R, (iii)-P, (iv)-S
3. c(i)-Q, (ii)-P, (iii)-R, (iv)-S
4. d(i)-S, (ii)-R, (iii)-P, (iv)-Q

Match each formula/term with its expression in the new Cartesian sign convention:

1. a(i)-R, (ii)-Q, (iii)-P, (iv)-S
2. b(i)-Q, (ii)-R, (iii)-P, (iv)-S
3. c(i)-R, (ii)-Q, (iii)-S, (iv)-P
4. d(i)-P, (ii)-Q, (iii)-R, (iv)-S

A school science club builds a solar furnace using a large concave mirror turned towards the Sun. To heat a small vessel of water as quickly as possible, where should the vessel be placed, and why?

1. aAt the centre of curvature, as the image of the Sun there is the same size as the Sun
2. bAt the principal focus, as the parallel rays from the Sun converge there to a point
3. cBetween the focus and the centre of curvature, as the image there is enlarged and bright
4. dAt the pole of the mirror, as the mirror surface itself gets the hottest

A swimming-pool lifeguard sees a swimmer's legs near the edge as if shorter than the actual depth — the pool 'looks' shallower from above. The phenomenon is BEST explained by:

1. aTotal internal reflection of light at the water surface
2. bRefraction of light from water (denser) to air (rarer); rays bend AWAY from normal making the legs appear closer to the surface
3. cLight is absorbed by water, so the legs only appear faintly
4. dLight travels faster in water than in air

A student wants to use a CONVEX lens of focal length 20 cm to read fine print as a magnifier. The fine print should be placed:

1. aWITHIN 20 cm (less than focal length) from the lens
2. bAt any distance between 20 cm and 40 cm from the lens
3. cAt a distance greater than 40 cm from the lens
4. dExactly at 40 cm from the lens

The radius of curvature of a concave mirror is 30 cm. Its focal length is:

1. a30 cm
2. b60 cm
3. c15 cm
4. d45 cm

An object 5 cm tall is placed 30 cm in front of a convex lens of focal length 20 cm. Image distance is \(+60\) cm. The magnification is:

1. a\(+0.5\)
2. b\(+2\) (erect, magnified)
3. c\(-0.5\)
4. d\(-2\) (inverted, magnified twice)

Refractive index of water is \(\frac{4}{3}\) and that of glass is \(\frac{3}{2}\). The refractive index of GLASS WITH RESPECT TO WATER is:

1. a0.889
2. b1.125
3. c1.5
4. d2.0

A ray of light falls obliquely on one face of a rectangular glass slab at an angle of incidence of \(40^\circ\) and comes out through the opposite parallel face. Which statement correctly describes the emergent ray?

1. aIt is parallel to the incident ray but shifted sideways
2. bIt continues along the same straight line as the incident ray
3. cIt bends towards the normal, so the angle of emergence is less than \(40^\circ\)
4. dIt is perpendicular to the incident ray

Why does a camera use a CONVEX lens (rather than a concave or plane lens) to form an image of a distant object?

1. aConvex lens diverges light, spreading it over the film
2. bConcave lens forms a real image which is more useful
3. cConvex lens converges light, forming a real image on the film
4. dA plane lens would give a sharper image

From the passage, when an object is at INFINITY, the camera's image forms at:

1. aTwice the focal length on the same side
2. bBehind the camera body
3. cAnywhere on the principal axis
4. dThe focal point of the lens

The camera lens in the passage has a focal length of 50 mm. It is used to photograph a flower 30 cm in front of it. Using the passage's lens formula, how far behind the lens must the film be?

1. a50 mm, the same as for a distant object
2. b100 mm, twice the focal length
3. c60 mm
4. dAbout 43 mm

What does a SMALL camera APERTURE do to the amount of light reaching the film?

1. aIncreases brightness because focused
2. bDecreases the amount of light, but increases depth of field (sharper range)
3. cHas no effect on light
4. dLets through only red light