# Moving Object, Stationary Lens

## Trending Questions

**Q.**A lens of focal length f forms an image of magnification n, The distance of object from the lens in terms of f and n is

- (1+n)f
- (1−n)fn
- fn
- nf(1−n)

**Q.**

A long-sighted person has a distance of distinct vision of $40cm$. Find the nature and the focal length of the lens used by him to read a book $20cm$ from the eye, using spectacles.

**Q.**

A hemispherical portion of the surface of a solid glass sphere (p rt: 1.5) of radius r is silvered to make the inner side reflecting. An object is placed on the axis of the hemisphere at a distance 3r from the centre of the sphere. The light from the object is refracted at the unsilvered part, then reflected from the silvered part and again refracted at the unsilvered part. Locate the final image formed.

**Q.**A convex lens forms a real image three times larger than the size object on a screen. Object and screen are moved until the image becomes twice the size of the object. If the shift of the object is 6 cm (away from the lens), the shift of screen is :

- 36 cm
- 72 cm
- 18 cm
- 9 cm

**Q.**

The photograph of a house occupies an area of 1.75 cm2 on a 35 mm slide. The slide is projected on to a screen, and the area of the house on the screen is 1.55 m2. What is the linear magnification of the projector-screen arrangement.

**Q.**The height of the image formed by a converging lens on a screen is 8 cm. For the same position of the object and screen again, an image of size 12.5 cm is formed on the screen by shifting the lens. The height of the object is (in cm) -

**Q.**An object is placed 12 cm to the left of a converging lens of focal length 8 cm. Another converging lens of 6 cm focal length is placed at a distance of 30 cm to the right of the first lens. The second lens will produce

- No image

- A real smaller image
- A real enlarged image

- A virtual enlarged image

**Q.**There is a small air bubble inside a thick lens of glass as shown in the figure. What is the distance between the images of the air bubble as seen by two observers, one in air and other in water?

(Given radius of curved surface is 5 cm)

- 1.5 cm
- 9 cm
- 4 cm
- 1 cm

**Q.**Find the maximum and minimum magnifying powers of a telescope. Focal length of the lenses used are 12.5 cm and 100 cm

- 10 and 8
- 12 and 8
- 18 and 12
- 22 and 12

**Q.**

A converging lens of focal length 20 cm and a diverging mirror of focal length 10 cm are placed 5 cm apart with their principal axes coinciding. Where should an object be placed so that its image falls on itself?

- −50 cm
- 100 cm
- 50 cm
- −100 cm

**Q.**A point object at 15 cm from a concave mirror of radius of curvature 20 cm is made to oscillate along the principal axis with amplitude 2 mm. The amplitude of its image will be

- 2mm
- 4mm
- 8mm
- 16mm

**Q.**Two lenses of power 25 D and −15 D are in contact with each other. Focal length of the combination will be

- 100 cm
- 15 cm
- 10 cm
- 80 cm

**Q.**Find out the value of object distance x, such that image will form at the object position.

(Assume lens to be thin)

- 10 cm
- 15 cm
- 25 cm
- 30 cm

**Q.**

A convex lens of focal length 20 cm and a concave lens of focal length 10 cm are placed 10 cm apart with their principal axes coinciding. A beam of light travelling parallel to the principal axis and having a beam diameter 5.0 mm, is incident on the combination.. Show that the emergent beam is parallel to the incident one. Find the beam diameter of the emergent beam.

**Q.**A X-ray tube operates at potential 15 kV. Findthe minimum wavelength of X-ray

**Q.**

Which property of a reflecting telescope determines its light-gathering or light-collecting power?

Elimination of extraneous light.

Size of the primary lens.

Obstruction of ultraviolet rays.

Apprehending white light better than any other color.

**Q.**A small object is placed 50 cm to the left of a thin convex lens of focal length 30 cm. A convex spherical mirror of radius of curvature 100 cm is placed to the right of the lens at a distance of 50 cm. The mirror is tilted such that the axis of the mirror is a an angle θ=30∘ to the axis of the lens, as shown in the figure.

If the origin of the coordinate system is taken to be at the centre of the lens, the coordinates (in cm) of the point (x, y) at which the image is formed are

- (25, 25√3)
- (1253, 25√3)
- (0, 0)
- (50−25√3, 25)

**Q.**A double convex lens made of glass (μ=1.5) has both radii of curvature of magnitude 20 cm. Incident rays parallel to the axis of the lens will converge at a distance L such that:

- L = 20 cm
- L = 10 cm
- L = 40 cm
- L=203cm

**Q.**A convex lens forms a real image three times larger than the object on a screen. Object and screen are moved until the image becomes twice the size of the object. If the shift of the object is 6 cm, the shift of screen in cm is

**Q.**The image for the converging beam after refraction through the curved surface is formed at

- 20 cm
- 1807 cm
- 403 cm
- 40 cm

**Q.**A thin convex lens of focal length 30.00 cm forms an image 2.00 cm high, of an object at infinity. A thin concave lens of focal length 20.00 cm is placed 26.00 cm from the convex lens on the side of the image. The height of the image now is

- 1.00 cm
- 1.25 cm
- 2.00 cm
- 2.50 cm

**Q.**A coordinate axis as shown below is kept infront of a converging lens at a distance 2f from it where f is the focal length of the lens, what is the approximate shapeof the image as seen by an observer on the other side of the lens at a distance 3f from it. Assume that x−axis is along the principle axis of the lens

**Q.**Find the minimum focal length of a normal human eye. If the distance of eyelens from retina is 2 cm

- 2 cm
- 1.85 cm
- 1.92 cm
- 1.76 cm

**Q.**A screen is placed 90 cm from an object . The image of the object on the screen is formed by convex lens at two different locations separated by 20 cm . Determine the focal length of the lens (b) suppose the object has a size of 10 cm, and in one case the image is half of its size. Determine image size when lens is displaced to second position

**Q.**An angular magnification of 30X is desired using an eye piece of focal length 5 cm and an objective lens. Find the magnifying power of objective lens. [Given angular magnification is achieved in case of normal adjustment]

- 6
- 7
- 8
- 9

**Q.**Which of the following graphs correctly shows the variation of magnetic field intensity (

*B*) with perpendicular distance (

*r*) for a thin long straight wire carrying a current?

निम्नलिखित में से कौनसा आरेख एक पतले लम्बे सीधे धारावाही तार के लिए लम्बवत् दूरी (

*r*) के साथ चुम्बकीय क्षेत्र तीव्रता (

*B*) के परिवर्तन को सही रूप से दर्शाता है?

**Q.**A lens forms a virtual, diminished image of an object placed at 2 m from it. The size of image is half of the object. Which one of the following statements is correct regarding the nature and focal length of the lens?

- Concave, |f|=1 m
- Convex, |f|=1 m
- Concave, |f|=2 m
- Convex, |f|=2 m

**Q.**In displacement method, the distance between object and screen is 96 cm. The ratio of lengths of two images formed by a converging lens placed between them is 4. Then

- Focal length of the lens is 64/3cm
- Ratio of the length of object to the length of shorter image is 2
- Distance between the two positions of the lens is 32cm
- When the shorter image is formed on screen, distance of the lens from the screen is 32cm

**Q.**An object and a screen are mounted on an optical bench and a converging lens is placed between them so that a sharp image is obtained on the screen. The linear magnification of the image is 25. The lens is now moved 30 cm towards the screen and a sharp image is again formed on the screen. Find the focal length of the lens.

- 14.3cm
- 1.2cm
- 14.6cm
- 14.9cm

**Q.**

The focal length of a convex lens is $30cm$and the size of the image is half of the object. The object distance is

$30cm$

$40cm$

$60cm$

$90cm$