Image Formation by Concave Lens

Q.

Magnification is -1 what type of mirror is it and the position of the image and the nature of the image is -

Q.

The rear view mirror of a car is a plane mirror. A driver is reversing his car at a speed of 2 $\frac{m}{s}$. The driver sees in his rear view mirror the image of the truck parked behind his car. The speed at which the image of the truck appears to approach the driver will be?

Q. Which type of lens is used to correct presbyopia ?

Q. What is the power of a convex lens of focal length 10 cm?

1. 0.1 D
2. -0.1 D
3. 10 D
4. -10 D

Q.

Two thin lenses are in contact and the focal length of the combination is $80cm$. If the focal length of one lens is $20cm$, then the power of the other lens will be

1. $-1.00D$

2. $1.66D$

3. $-3.75D$

4. $4.00D$

Q. A needle 4 cm high is placed in front of a lens. Image of the needle is real , inverted and 6 cm high , when distance between the needle and its image is 20 cm. Find the focal leght of lens and also write the type if this lens.

Q. A student has to project a 3 times magnified image of the candle flame on a wall.name the type of lens required for this purpose.If the candle flame is at a distance of 6m from the wall, find the focal length of the lens.

Q.

An object is placed perpendicular to principal axis of a convex lens of focal length 20cm.the distance of object from lens is 30cm

Find the position, magn magnifica and Nature of image

Q. The characteristic(s) of an image formed by the concave lens when an object is placed beyond 2f is/are:
(f is the focal length of the lens)

1. Virtual and erect
2. Magnified
3. Diminished
4. Real and inverted

Q.

A concave lens produces an image 20 cm from the lens for an object placed 30 cm from the lens. The focal length is

1. -60 cm

2. -90

3. +60 cm

4. -40 cm

Q. Which of the following statements is true about concave lenses?

1. They always form real images.
2. They always form enlarged images.
3. They always form virtual images.
4. They always form inverted images.

Q.

The distance at which an object should be placed from a thin convex lens of focal length 10 cm to obtain a virtual image of double of its size is

1. 5.5 cm

2. - 5 cm

3. 15 cm

4. -10cm

Q. A concave lens always forms a diminished, image.

1. virtual and inverted
2. real and inverted
3. virtual and erect
4. real and erect

Q. Derive mirror formula when object is placed b/w (1) pole P and principal focus f in a concave mirror (2)in convex mirror

Q.

The image of a distant object is obtained on a screen by using a concave mirror. the focal length of the mirror can be determined by measuring the distant between

A) the object and the mirror

B) the object and the screen

C) the mirror and the screen

D) the mirror and the screen as well as the between the object and the screen

Q.

When a concave mirror is placed facing the sun, the sun rays converge to a point 15 cm from the mirror. Now, an erect 2 cm long pin is placed 30 cm away on the principal axis of the mirror. Where a card should be placed so that the image of the pin can be taken on the card? What would be the nature and height of the image?

Q.

The image formed by a convex lens is observed to be virtual, erect and larger than the object. then the position of the object should be?

Q.

Which lens always forms diminished and erect image?

Q.

A 2 cm long pin is placed perpendicular to the principal axis of a convex lens of focal length 15 cm at distance of 25 cm from the lens. Find the position of image and its size. [3 MARKS]

Q. find the position and nature of the image of an object of height 3 cm when placed 60 cm from a convex mirror of focal length 15cm

Q.

Define the term principal focus of concave Lens

Q.

A virtual image, we always say, cannot be caught on a screen. Yet when we ‘see’ a virtual image, we are obviously bringing it on to the ‘screen’ i.e., retina of our eye. Is there a contradiction? [3 MARKS]

Q. A lens having two spherical surface bulging outward is called.

1. concave lens
2. convex lens
3. plano-convex lens
4. plano-concave lens

Q.

When an object is placed at the principal focus of a concave mirror, the image is formed at...............

Q.

An object is placed at a distance of 20 cm from a convex lens of focal length 10 cm. The image is formed on the other side of the lens at a distance:

1. 30 cm
2. 20 cm
3. 10 cm
4. 40 cm

Q.

Can a concave lens form an image of size two times that of the object ? Give reason.

Q.

(a) Name the lens which always forms an erect and virtual image.

(b) State whether the image in part (a) is magnified or diminished.

Q.

Question 10
An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.

Q. An object of height 10cm is kept at a distance of 150cm in front of a concave mirror having radius of curvature 2m. What is the nature, height and distance of image formed by the mirror ?

Q. A thin lens is made with a material having refractive index $\mu =1.5$, both the sides are convex. It is dipped in water $(\mu =1.33)$. It will behave like

1. a convergent lens
2. a divergent lens
3. a rectangular slab
4. a prism