Find the odd one out and give its explanation. Simple microscope, Compound microscope, Telescope, Prism - Science and Technology 1


Find the odd one out and give its explanation.


  • Simple microscope

  • Compound microscope

  • Telescope

  • Prism





Prism disperses light while other optical instruments produce magnified images of objects.

Concept: Convex Lens
  Is there an error in this question or solution?
Chapter 7: Lenses - Find odd one out.


Complete the following table:

Instrument Number of Convex
Simple Microscope .............. ..............
Compound Microscope .............. ..............
Telescope .............. ..............

A beam of light travelling in a rectangular glass slab emerges into air. Draw a ray-diagram indicating the change in its path.

The diagram given alongside shows a ray of light entering a rectangular block of glass.

(a) Copy the diagram and draw the normal at the point of entry.
(b) Draw the approximate path of the ray of light through the glass block and out of the other side.

Draw a labelled ray diagram to show how a ray of light passes through a parallel sided glass block:  

if it hits the glass block at 90° (that is, perpendicular to the glass block) 

State any two uses of convex lenses.

 List some things that convex lens and concave mirror have in common.  

An object 4 cm high is placed at a distance of 10 cm from a convex lens of focal length 20 cm. Find the position, nature and size of the image.

What kind of lens can form: 

 an inverted magnified image? 

Define the term principal axis of a lens.

The diagram alongside shows a lens as a combination of a glass block and two prisms.  Name the lens formed by the combination. 

A convex lens forms an image of an object equal to the size of the object.state two more characteristics of the image.

A teacher sets up the stand carrying a convex lens of focal length 15 cm at 42.7 cm mark on the optical bench. He asks four students A, B, C and D to suggest the position of screen on the optical bench so that a distinct image of a distant tree is obtained almost immediately on it. The positions suggested by the students were as

A. 12.7 cm

B. 29.7 cm

C. 57.7 cm

D. 72.7 cm

The correct position of the screen was suggested by

(a) A

(b) B

(c) C

(d) D

i. Which type of microscope has the arrangement of lenses shown in the  adjoining figure?
ii. Label the figure correctly.
iii. Write the working of this microscope.
iv. Where does this microscope used?
v. Suggest a way to increase the efficiency of this microscope.

The image obtained while finding the focal length of convex lens is ....................

Observe the following figure and answer the questions.

a) Which optical instrument shows arrangement of lenses as shown in the figure?
b) Write in brief the working of this optical instrument.
c) How can we get different magnifications in this optical instrument?
d) Draw the figure again and labelled it properly

Yesh find out F1 and F2 of symmetric convex lens experimentally then which conclusion is true.

Observe the following figure and complete the table:

Points Answer
(i) Position of the object  
(ii) Position of the image  
(iii) Size of the image   
(iv) Nature of the image  

A convex lens produces an image on a screen twice the size of the object. The distance between the object and screen is 45 cm. Find the distance of the lens from the object and its focal length by drawing a ray diagram.

(a) What type of a lens can be used as a magnifying glass?
(b) Show by a ray diagram the formation of a real image by simple magnifying lens.

State two applications each of a convex lens and concave lens.

If an object is placed in front of a convex lens beyond 2F1, then what will be the position, relative size, and nature of an image which is formed? Explain with a ray diagram.

Rewrite the following statement by selecting the correct option:
The power of a convex lens is 2.5 dioptres. Its focal length is ______________.

Point out the difference between a convex lens and a concave lens.

Write the three characteristics of the image formed by a convex lens of focal length 20 cm for the object at distance (i) 10 cm, (ii) 30 cm, (iii) 40 cm, (iv) 60 cm from the lens.

In sunglasses, both of its surfaces are curved, yet their behaviour is neither like a convex lens nor like a concave lens. State the reason.

An object is placed in front of a convex lens such that the image formed has the same size as that of the object. Draw a ray diagram to illustrate this.

Can one bum a piece of paper in daylight by just using a convex lens instead of a match or any direct flame? Support your answer with the help of an appropriate ray diagram.

For a specific glass lens f = 0.5 m. This is the only information given to the student. Which type of lens is given to him and what is its power?

_______ times larger images can be obtained by using a simple microscope.

_______ is a combination of two convex lenses with small focal length.

Object at 2F1 of a convex lens : Image at 2F2 : : Object at F1 : _______

Simple microscope : Number of convex lens one : : compound microscope : _______

Find the odd one out and give its explanation.

Write the name.

The lens used in simple microscope.

Write scientific reason.

Adults need bifocal lens spectacle.

Observe the given figure and answer the following questions.

  1. Where is the above type of lens construction used?
  2. What type of image is formed by an objective lens?
  3. What happens instead of placing at Fo if the object is placed in between O and Fo?

Differentiate convex lens and concave lens.

  1. In which type of microscope do you find the lens arrangement as shown in the following diagram?
  2. Write about the working and the use of this microscope.

The above images are that of a specialized slide projector. Slides are small transparencies mounted in sturdy frames ideally suited to magnification and projection since they have a very high resolution and a high image quality. There is a tray where the slides are to be put into a particular orientation so that the viewers can see the enlarged erect images of the transparent slides. This means that the slides will have to be inserted upside down in the projector tray.

To show her students the images of insects that she investigated in the lab, Mrs. Iyer brought a slide projector. Her slide projector produced 500 times enlarged and inverted image of a slide on a screen 10 m away.

a. Based on the text and data given in the above paragraph, what kind of lens must the slide projector have?

b. If v is the symbol used for image distance and u for object distance then with one reason state what will be the sign for `"𝑣"/"𝑢"` in the given case?

c. A slide projector has a convex lens with a focal length of 20 cm. The slide is placed upside down 21 cm from the lens. How far away should the screen be placed from the slide projector’s lens so that the slide is in focus?


c. When a slide is placed 15 cm behind the lens in the projector, an image is formed 3 m in front of the lens. If the focal length of the lens is 14 cm, draw a ray diagram to show image formation. (not to scale)

Distinguish between Concave lens and Convex lens.

Distinguish between:

Concave lens and Convex Lens

Distinguish between Concave lens and Convex Lens.

Distinguish between:

Concave lens and Convex Lens

Distinguish between:

Concave lens and Convex Lens


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