Image Formation

Q.

A convex lens forms a real and inverted image of a needle at a distance of $50cm$ from it. Where is the needle placed in front of the convex lens if the image is equal to the size of the object? Also, find the power of the lens.

Q.

The power of a lens is 5D. Find its focal length.

Q.

What are photoreceptors?

Q. In the given figure , find the lateral shift produced by the glass slab.

1. $\sqrt{3}\text{m}$
2. $\frac{1}{\sqrt{2}}\text{m}$
3. $\frac{1}{\sqrt{3}}\text{m}$
4. $\sqrt{2}\text{m}$

Q.

Yellow colour is formed by mixing the red and green.

1. True
2. False

Q.

What happens if we move from a dark room into bright sunshine suddenly? Explain your answer in terms of response to stimulus.

Q.

Name the coloured pigment present in rods and cones.

Q.

A person suffering from myopia (near-sightedness) was advised to wear a corrective lens of power - 2·5 D. A spherical lens of the same focal length was taken in the laboratory. Draw a ray diagram to show the position and nature of the image formed at a distance of 10 cm from the lens.

Q. A myopic person can not see objects lying beyond $2m$. The focal length and power of the lens required to remove this defect will be

1. $1$ m and $0.5$ D
2. $-2$ m and $-0.5$ D
3. $0.5$ m and $0.5$ D
4. $-0.5$ m and $0.5$ D

Q.

What power of a lens will change the reading distance from 1 m to 0.25 m?

Q.

The distance between an object and a screen is $100cm$. A lens produces an image on the screen when the lens is placed at either of the positions $40cm$ apart. What will be the power of lens, approximately?

Q.

State the exact location of yellow spot.

Q. A man cannot see an object closer than $1\text{m}$ from the eye clearly. What is the power of the corrective lens, he should use?

1. $+3\text{D}$
2. $-3\text{D}$
3. $+2\text{D}$
4. $-2\text{D}$

Q.

A needle placed $45cm$ from a lens forms an image on a screen placed $90cm$ on the other side of the lens. What is the power of the lens?

1. $+10D$

2. $-10D$

3. $+3.33D$

4. $-3.33D$

Q. A person suffering from myopia cannot see clearly beyond a distance of $1.5\text{m}$. Calculate the power of the lens used to correct this defect.

1. $-1\text{D}$
2. $1.5\text{D}$
3. $0.67\text{D}$
4. $1.25\text{D}$

Q.

Differentiate between the rod cells and cone cells (on the basis of pigment).

Q. A man is running towards a plane mirror at a speed of $2m{s}^{-1}$. How fast does he see himself running towards his image?

1. 2m/s
2. 4m/s
3. 5m/s
4. 3m/s

Q. A myopic person can not see objects lying beyond $2m$. The focal length and power of the lens required to remove this defect will be

1. $1$ m and $0.5$ D
2. $-2$ m and $-0.5$ D
3. $0.5$ m and $0.5$ D
4. $-0.5$ m and $0.5$ D

Q.

Which of the following helps us to distinguish colours?

1. Rods

2. Rhodopsin

3. Cones

4. All of the above

Q. A green light is incident from the water to the air - water interface at the critical angle $\left(\theta \right)$. Select the correct statement.

1. The spectrum of visible light whose frequency is less than that of green light will come out of the air medium.
2. The entire spectrum of visible light will come out of the water at various angles to the normal.
3. The entire spectrum of visible light will come out of the wtaer at an angle of ${90}^{\circ }$ to the normal.
4. The spectrum of visible light whose frequency is more than that of green light will come out to the air midium.

Q. A large square container with thin transparent vertical walls and filled with water (refractive
index $\frac{4}{3}$) is kept on a horizontal table. A student holds a thin straight wire vertically inside the
water $12\text{cm}$ from one of its corners, as shown schematically in the figure. Looking at the wire from this corner, another student sees two images of the wire, located symmetrically on each side of the line of sight as shown. The separation (in $\text{cm})$ between these images is

Q. An observer can see through a small hole on the side of a jar $($radius $15\text{cm})$ at a point at height of $15\text{cm}$ from the bottom (see figure). The hole is at a height of $45\text{cm}.$ When the jar is filled with a liquid up to a height of $30\text{cm}$ the same observer can see the edge at the bottom of the jar. If the refractive index of the liquid is $\frac{N}{100}$ where $N$ is an integer. The value of $N$ is ____.

Q. Pigment in the cone cells of man responsible for detecting red colour is

1. Erythrolabe
2. Chlorolabe
3. Cyanolabe
4. Rhodopsin

Q. A container contains water up to a height of $20\text{cm}$ and there is a point at the centre of the bottom of the container. A rubber ring of radius $R$ floats centrally on the water. The ceiling of the room is $2\text{m}$ above the water surface. Then, choose the correct option(s):

1. Maximum value of $R$ of the ring for which the ring forms a shadow on the ceiling is $22.6\text{cm}$.
2. If $R=15\text{m}$, radius of the shadow of the ring on the ceiling is $2.8\text{m}$.
3. Maximum value of $R$ for which the shadow of the ring forms on the ceiling is $11.3\text{cm}$.
4. If $R=15\text{m}$, radius of the shadow of the ring on the ceiling is $1.4\text{m}$.

Q. Animals perceiving coloured images are

1. Primates
2. All of the above
3. Birds
4. Lizards and snakes

Q. Write about your experience in the following two cases.
a. Enter into a dark room from a very bright place. What happens?
b. Sit in a dark room for some time and go into a bright light room. What happens?

Q. When we move from dark to light, we fail to see for some time but soon the visibility becomes normal. It is

1. Adaptation
2. Mutation
3. Photoperiodism
4. Accommodation

Q.

The illuminance of a small area changes from 900 lumen $m^{-}1$ to 400 lumen $m^{-}2$ when it is shifted along its normal by 10 cm. Assuming that it is illuminated by a point source placed on the normal, find the distance between the source and the area in he original position .

Q. Write One property of the black body with rough surface

Q. The part of the human eye where rod cells and cone cells are located is the

1. Retina
2. Cornea
3. Choroid
4. Sclera