Refraction of Refraction Science - Refraction of Refraction

A convex lens has a focal length of 10cm. At which of the following position should an object be placed so that this convex lens may act as a magnifying glass?

A lens of focal length 12cm forms an erect image three times the size of the object. The distance between the object and image is:

An object is 0.09m from a magnifying lens and the image is formed 36cm from the lens. The magnification produced is:

The power of a converging lens is 4.5D and that of a diverging lens is 3D. The power of this combination of lenses placed close together is:

Only one of the following applies to a concave lens. This is:

Fill in the following blanks with suitable word:
A convex lens _________ rays of light, whereas a concave lens __________ rays of light.

Fill in the following blanks with suitable word:
Lenses refract light to form images, a _________ lens can form both real and virtual images, but a diverging lens forms only ________ images.

Fill in the following blanks with suitable words:
The image in a convex lens depends upon the distance of the __________ from the lens.

Fill in the following blanks with suitable words:
The reciprocal of the focal length in metres gives you the _____________ of the lens, which is measured in _____________.

Fill in the following blank with a suitable word:
When a ray of light goes from air into a clear material, you see the ray bend. How much the ray bends is determined by the ___________ of the material.

A beam of light travelling in a rectangular glass slab emerges into air. Draw a ray-diagram indicating the change in its path.

A ray of light goes from water into air. Will it bend towards the normal or away from the normal?

Which of the two has a greater power:
A lens of short focal length or a lens of large focal length?

What is the nature of the image formed by a convex lens if the magnification produced by the lens is +3?

Where should an object be placed in front of a convex lens so as to obtain its real, inverted and magnified image?

A lens has a focal length of, -10cm. What is the power of the lens and what is its nature?

List some things that convex lens and concave mirror have in common.

What is the position of image when an object is placed at a distance of 10cm from a convex lens of focal length 10cm?

An object is placed at the following distance from a convex lens of focal length 15cm:

1. 35cm
2. 30cm
3. 20cm
4. 10cm

Which position of the object will produce:

1. A magnified real image?
2. A magnified virtual image?
3. A diminished real image?
4. An image of same size as the object?

A doctor has prescribed a corrective lens of power, -1.5D. Find the focal length of the lens. Is the prescribed lens diverging or converging?

Which type of lens is:

1. A converging lens, and which is.
2. A diverging lens? Explain your answer with diagrams.

With the help of a labelled diagram, explain why a tank full of water appears less deep than it actually is.

A concave lens has focal length 15cm. At what distance should the object from the lens be placed so that it forms an image at 10cm from the lens? Also find the magnification produced by the lens.

A concave lens of 20cm focal length forms an image 15cm from the lens. Compute the object distance.

The optical prescription for a pair of spectacles is:
Right eye: 3.50D, Left eye: 4.00D

1. Are these lenses thinner at the middle or at the edges?
2. Which lens has a greater focal length?
3. Which is the weaker eye?

An object is placed 10cm from a lens of focal length 5cm. Draw the ray diagrams to show the formation of image if the lens is:

1. Converging, and
2. Diverging.

Construct ray diagrams to illustrate the formation of a virtual image using:

1. A converging lens, and.
2. A diverging lens.

An object placed 4cm in front of a converging lens produces a real image 12cm from the lens.

1. What is the magnification of the image?
2. What is the focal length of the lens?
3. Draw a ray diagram to show the formation of image. Mark clearly F and 2F in the diagram.

Which one of the following materials cannot be used to make a lens?

1. Water.
2. Glass.
3. Plastic.
4. Clay.

Which of the following can make a parallel beam of light from a bulb falls on it?

1. Concave mirror as well as concave lens.
2. Convex mirror as well as concave lens.
3. Concave mirror as well as convex lens.
4. Concave mirror as well as convex lens.

Which of the following can form a virtual image which is always smaller than the object?

1. A plane mirror.
2. A convex lens.
3. A concave lens.
4. A concave mirror.

When sunlight is concentrated on a piece of paper by a spherical mirror or lens, then a hole can be burnt in it. For doing this, the paper must be placed at he focus of:

1. Either a convex mirror or convex lens.
2. Either a concave mirror or concave lens.
3. Either a concave mirror or convex lens.
4. Either a convex mirror or concave lens.

When a ray of light travelling in glass enters into water obliquely:

1. It is refracted towards the normal.
2. It is not refracted at all.
3. It goes along the normal.
4. It is refracted away from the normal.

Fill in the following blank with a suitable word:
When a ray of light goes from air into a clear material, you see the ray bend. How much the ray bends is determined by the ___________ of the material.

Fill in the following blanks with suitable words:
The reciprocal of the focal length in metres gives you the _____________ of the lens, which is measured in _____________.

Fill in the following blanks with suitable words:
The image in a convex lens depends upon the distance of the __________ from the lens.

Fill in the following blanks with suitable words:
Parallel rays of light are refracted by a convex lens to a point called the _________.

Fill in the following blanks with suitable words:
Light travelling along a normal is ___________.

Write the relation between the angle of incidence and the angle of refraction for a medium.

Why does a ray of light bend when it travels from one medium to another?

Which typie of lens has (a) a positive power, and (b) a negative power?

Which type of lenses are:

1. Thinner in the middle than at the edges?
2. Thicker in the middle than at the edges?

Which phenomenon of light makes the water to appear shallower than it really is?

Your eye contains a convex lens. Why is it unwise to look at the sun?

Write the formula for a lens connecting image distance (υ), object distance (u) and the focal length (f). How does the lens formula differ from the mirror formula?

Write down the magnification formula for a lens in terms of object distance and image distance. How does this magnification formula for a lens differ from the corresponding formula for a mirror?

With the help of a labelled diagram explain how a convex lens converges a beam of parallel light rays.

With the help of a labelled diagram, explain how a concave lens diverges a beam of parallel light rays.

With the help of a labelled diagram, explain why a tank full of water appears less deep than it actually is.

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.

Which type of lens is:

1. A converging lens, and which is.
2. A diverging lens? Explain your answer with diagrams.

When an object is placed 10cm in front of lens A, the image is real, inverted, magnified and formed at a great distance. When the same object is placed 10cm in front of lens B, the image formed is real, inverted and same size as the object:

1. What is the focal length of lens A?
2. What is the focal length of lens B?
3. What is the nature of lens A?
4. What is the nature of lens B?

What is the effect on the size and position of the image of moving the object:

1. Towards the lens, and
2. Away from the lens?

The speed of light in vacuum and in two different glasses is given in the table below:

Medium	Speed of light
Vacuum Flint glass Crown glass	3.00× 108m/ s 1.86× 108m/ s 1.97× 108m/ s

1. Calculate the absolute refractive indexes of flint glass and crown glass.
2. Calculate the relative refractive index for light going from crown glass to flint glass.

The speed of light in air is 3 × 10⁸m/ s. In medium X its speed is 2 × 10⁸m/ s and in medium Y the speed of light is 2.5 × 10⁸m/ s. Calculate:

1. air ⁿx
2. air ⁿy
3. X ⁿy

Draw ray diagrams to represent the nature, position and relative size of the image formed by a convex lens for the object placed:

1. At 2F₁
2. between F and the optical centre O of the lens.

Which of the above two cases shows the use of convex lens as a magnifying glass ? Give reasons for your choice.

Construct ray diagrams to illustrate the formation of a virtual image using:

1. A converging lens, and.
2. A diverging lens.

A student did an experiment with a convex lens. He put an object at different distances 25cm, 30cm, 40cm, 60cm and 120cm from the lens. In each case he measured the distance of the image from the lens. His results were 100cm, 24cm, 60cm, 30cm and 40cm, respectively. Unfortunately his results are written in wrong order:

1. Rewrite the image distances in the correct order.
2. What would be the image distance if the object distance was 90cm?
3. Which of the object distances gives the biggest image?
4. What is the focal length of this lens?