Image in Thin Lens by Ray Tracing

Q. The optic axis of a thin equiconvex lens is the x – axis. The co-ordinates of a point object and its image are ($-40\text{cm}$, $1\text{cm}$) and ($50\text{cm}$, $-2\text{cm}$) respectively. The lens is located at x= -n cm. Find n

Q. A point object O is placed on the principal axis of a convex lens of focal length 20 cm at a distance of 40 cm to the left of it. The diameter of the lens is 10 cm. If the eye is placed 60 cm to the right of the lens at a distance h below the principal axis, then the maximum value of h to see the image will be

1. 0
2. 5 cm
3. 2.5 cm
4. 10 cm

Q.

A screen is placed 90 cm from an object. The image of the object on the screen is formed by a convex lens at two different locations separated by 20 cm. Determine the focal length of the lens.

Q.

A student wants to project the image of a candle flame on the walls of the school laboratory by using a lens At what distance in terms of focal length F of the lens should be placed the candle flame so as to get (a) a magnified, and (b) a diminished imaged respectively on the wall?

Q. A beam of light converges to a point $P$. A concave lens of focal length $16cm$ is placed in the path of the convergent beam $12cm$ from $P$. How far from the lens does the beam converge?

1. $12cm$
2. $7.5cm$
3. $36cm$
4. $48cm$

Q.

3 lenses L1, L2 and L3 each of focal length 30 cm are placed coaxially .an object is held at 60cm from the optical centre of lens L1.the final image is formed at the focus os L3.Calculate the separation between 1) L1 and L2 2) L2 and L3

Q. An object of length $2.0\text{cm}$ is placed perpendicular to the principal axis of a convex lens of focal length $12.0\text{cm}$. Find the size of the image if the object is at the distance of $8.0\text{cm}$ from the lens.

1. $4.0\text{cm}$
2. $6.0\text{cm}$
3. $8.0\text{cm}$
4. $9.0\text{cm}$

Q. A diverging lens of focal length $20cm$ having refractive index $1.5$ is immersed in a liquid of refractive index $3$. The focal length and nature of the lens in liquid is

1. $20cm$ divergent
2. $20cm$ convergent
3. $10cm$ divergent
4. $10cm$ convergent

Q. A diverging lens with magnitude of focal length $25cm$ is placed at a distance of $15cm$ from a converging lens of magnitude of focal length $20cm$. A beam of parallel light falls on the diverging lens. The final image formed is

1. Real and at a distance of $6cm$ from the convergent lens.
2. Real and at a distance of $40cm$ from the convergent lens.
3. Virtual and at a distance of $40cm$ from the convergent lens.
4. Real and at a distance of $40cm$ from the divergent lens.

Q. The sun's diameter is $1.4\times {10}^{9}m$ and its distance from the earth is ${10}^{11}m.$ The diameter of its image, formed by a convex lens of focal length 2m will be

1. 0.7 cm
2. 1.4 cm
3. 2.8 cm
4. Zero (i.e. point image)

Q. 16. The exposure time of a camera lens at f/2.8 setting is 1/200s .The correct time of exposure at f/5.6 is…

Q. The objective of an astronomical telescope has a focal length of $100\text{cm}$. The telescope is focused for normal vision of distant objects when tube length is $1.1\text{m}$. Find magnifying power of the telescope.

Q.

A thin lens made of a material of refractive index ${\mu }_2$, has a medium of refractive index ${\mu }_1$ on one side and a medium of refractive index ${\mu }_2$ on the other side. The lens is biconvex and the two radii of curvature have equal magnitude R. A beam of light travelling parallel to the principal axis is incident on the lens. Where will the image be formed if the beam is incident from

(a) The medium ${\mu }_1$, and

(b) From the medium ${\mu }_3$ ?

Q.

An object at a distance of $20m$ from a convex lens of focal length $0.3m$. The lens forms an image of the object. If the object moves away from the lens at a speed of $5\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right.$, the speed and direction of the image will be

1. $3.22\times {10}^{-3}\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right.$ towards the lens

2. $2.26\times {10}^{-3}\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right.$ away from the lens

3. $1.16\times {10}^{-3}\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right.$ towards the lens

4. $0.92\times {10}^{-3}\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right.$ away from the lens

Q. If we cut a convex lens half along the principle axis what will be focal length and how it is different from the lens which is cut perpendicular to the axis? ARE THIS QUESTION ARE EASY OR DIFFICULT?

Q. A thin convex lens is cut into two parts in different ways that are arranged in four manners as shown. Which arrangement will give maximum optical power ?

1. 
2. 
3. 
4. 

Q. 62. When a ray of light strikes a plane mirror at an angle of 15 degree with the mirror, what will be the angle through which the is deviated?

Q.

A convex lens produces a double size real image when an object is placed at a distance of 18 cm from it. Where should the object be placed to produce a triple size real image ?

Q.

A pin of length 2.00 cm is placed perpendicular to the principal axis of a converging lens. An inverted image of size 1.00 cm is formed at a distance of 40.0 cm from the pin. Find the focal length of the lens and its distance from the pin.

Q.

A convex lens has a focal length of 10 cm. Find the location and nature of the image if a point object is placed on the principal axis at a distance of

(a) 9.8 cm

(b) 10.2 cm from the lens.

Q.

An object of length 2.0 cm is placed perpendicular to the principal axis of a convex lens of focal length 12 cm. Find the size of the image if the object is at a distance of 8.0 cm from the lens.

1. 8 cm

2. 4 cm

3. 6 cm

4. 10 cm

Q. A convex lens of focal length $f$ is cut into two halves as shown. Light rays parallel to the principal axis are incident on one half of the lens (say $L_1$) This will form an image at

1. $f$
2. $\frac{f}{2}$
3. $f$
4. $\frac{f}{4}$

Q. An object is at a distance of $20\text{m}$ from a convex lens of focal length $0.3\text{m}$. The lens forms an image of the object. If the object moves away from the lens at a speed of $5{\text{ms}}^{-1}$, the speed and direction of the image will be:

1. $2.26\times {10}^{-3}{\text{ms}}^{-1}$ away from the lens
2. $0.92\times {10}^{-3}{\text{ms}}^{-1}$ away from the lens
3. $3.22\times {10}^{-3}{\text{ms}}^{-1}$ towards the lens
4. $1.16\times {10}^{-3}{\text{ms}}^{-1}$ towards the lens

Q.

Two convex lenses, each of focal length 1.0 cm, are placed at a separation of 15 cm with their principal axes coinciding.

(a) Show that a light beam coming parallel to the principal axis diverges as it comes out of the lens system.

(b) Find the location of the virtual image formed by the lens system of an object placed far away.

(c) Find the focal length of the equivalent lens. (Note that the sign of the focal length is positive although the lens system actually diverges a parallel beam incident on it.)

Q. An object A is moving towards a converging lens as shown in the figure. If object is moving with speed $5\text{m/s}$, find the average velocity of image in next 4 seconds.

1. $5\text{cm/sec}$
2. $\frac{5}{3}\text{cm/sec}$
3. $20\text{cm/sec}$
4. $15\text{cm/sec}$

Q.

An object of length 2.0 cm is placed perpendicular to the principal axis of a convex lens of focal length 12 cm. Find the size of the image if the object is at a distance of 8.0 cm from the lens.

1. 8 cm

2. 4 cm

3. 6 cm

4. 10 cm

Q. Two half lenses $L_1({\mu }_1=1.4)$ & $L_2({\mu }_2=1.5)$ having radius of the curvature $R=20\text{cm}$ are placed together as shown. Find the position of the image of the parallel beam of light with respect to the common principal axis.

1. $100/7\text{cm}$
2. $200/9\text{cm}$
3. $31.2\text{cm}$
4. $21.8\text{cm}$

Q. Four lenses L1, L2­, L3 and L4 having focal length 5 cm, 7 cm, 20 cm and 100 cm respectively are provided. The lenses most likely used as objective and eyepiece to construct a compound microscope are respectively

Q.

Sudha finds out that the sharp image of the window pane of her science laboratory is formed at a distance of $15cm$ from the lens. She now tries to focus the building visible to her outside the window instead of the window pane without disturbing the lens. In which direction will she move the screen to obtain a sharp image of the building? What is the approximate focal length of this lens?

Q.

Which of the following diagrams correctly represents the ray of light passing through the optical center?

1. 

2. 

3. 

4.