The power of a combination of two lenses X and Y is 5D. If the focal length of lens X be 15cm:
- Calculate the focal length of lens Y.
- State the nature of lens Y.
Download our app for free and get started
- $\text{P}=\text{P}_\text{x}+\text{P}_\text{y}$
$5=\frac{100}{15}+\frac{\text{1}}{\text{f}_\text{y}}$
$\frac{\text{1}}{\text{f}_\text{y}}=5-\frac{100}{15}$
$=\frac{-25}{15}$
${\text{f}_\text{y}}=-0.6\text{m}=-60\text{cm}$
- Lens Y is a concave lens since it has negative focal length.
Download our appand get started for free
Experience the future of education. Simply download our apps or reach out to us for more information. Let's shape the future of learning together!No signup needed.*
Similar Questions
- 1View SolutionSudha 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?
- 2View SolutionDraw the ray diagram in your answer book and show the formation of image of object AB with suitable rays. Mention the position and nature of image.
- 3View SolutionAn erect image 2.0cm high is formed 12cm from a lens, the object being 0.5cm high. Find the focal length of the lens.
- 4View SolutionDraw ray diagrams to show the formation of three times magnified (a) real, and (b) virtual image of an object by a converging lens. Mark the positions of O, F and 2F in each diagram.
- 5View SolutionA dentist’s mirror has a radius of curvature of 3cm. How far must it be placed from a small dental cavity to give a virtual image of the cavity that is magnified five times?
- 6View SolutionThe magnification of an image formed by a lens is – 1. If the distance of the image from the optical centre of the lens is 35 cm, where is the object placed ? What is the nature and focal length of the lens? If the object is displaced 20 cm towards the optical centre of the lens, where would the image be formed and what will be its nature? Draw a ray diagram to justify your answer.
- 7View SolutionA convex lens of focal length 25cm and a concave lens of focal length 10cm are placed in close contact with each other. Calculate the lens power of this combination.
- 8View Solution
- Draw a diagram to show how a converging lens focusses parallel rays of light?
- How would you alter the above diagram to show how a converging lens can produce a beam of parallel rays of light.
- 9View SolutionWhat is a spherical mirror? Distinguish between a concave mirror and a convex mirror.
- 10View SolutionAn object of size 7.0cm is placed at a distance of 27cm in front of concave mirror of focal length 18cm. At what distance from the mirror should a screen be placed so that a sharply focused image can be obtained? Find the size and the nature of the image.