The Instrument Used to Observe Planets. - Science and Technology 1

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One Line Answer
The instrument used to observe planets.
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Solution

The instrument used to observe planets is the telescope.

Concept: Lens
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RELATED QUESTIONS

Show by a ray diagram that a diverging lens cannot form a real image of an object placed anywhere on its principal axis.


Draw a ray diagram to show how a converging lens can form an image of the sun. Hence give a reason for the term ‘burning glass’ for a converging lens used in this manner.


Match the columns in the following table and explain them.

Column 1 Column 2 Column 3
Farsightedness
Nearby object can be seen clearly
Bifocal lens
Presbyopia Far away object can be seen clearly Concave lens
Nearsightedness Problem of old age Convex lens

Distinguish between:

Farsightedness and Nearsightedness.


Make the correct choices in the following items : 

A converging lens B has the same focal length as a converging lens A, but only half the diameter, Both lens are used, separately, to form two images of building on a screen. which one of the follwing statements about the images is correct?

 


Aniket from Std. X uses spectacles. The power of the lenses in his spectacles is - 0.5 dioptre.
Answer the following questions:
  1. State the type of lenses used in his spectacles.
  2. Name the defect of vision Aniket is suffering from.
  3. Find the focal length of the lenses used in his spectacles.

We can burn a piece of paper by focussing the sun rays by using a particular type of lens. Name the type of lens used for the above purpose.


A converging lens is used to obtain an image of an object placed in front of it. The inverted image is formed between F2 and 2F2 of the lens. Where is the object placed?


From the nature of the refracted rays, shown in the diagram interpret the nature of the lens represented by the dotted line.


Draw a ray diagram to show the formation of an inverted and diminished image of an object by a lens. Name the lens used. State the position of the object with respect to the lens used. State one more characteristic of the image.


Draw the ray diagrams of a converging lens, when the object is placed at 2F on the principal axis. Write down the nature, position, and size of the image in both cases. Use only two rays in the diagrams.


Write down the characteristic of the image formed when the object is between F and the lens?


Define the principal axis.


In the convex lens if an object is placed at 2 F1, the image is formed at ______.


Find the odd one out and give its explanation.


Find the odd one out and give its explanation.


When the incident ray is parallel to the principal axis, the refracted ray passes through the principal focus.


Write an Explanation.

Centre of curvature of the lens


Write an Explanation.

The optical centre of the lens


Write law in a given figure.


Write law in a given figure.


Choose the correct option from the bracket and complete the stanza.

(colour blind, actual, conical, light-sensitive, rodlike, colours)

The retina in our eyes is made up of many _______ cells. These cells are shaped like a rod and like a cone. The _______ cells respond to the intensity of light and give information about the brightness or dimness of the object to the brain. The _______ cells respond to the colour and give information about the colour of the object to the brain. Brain processes all the information received and we see the _______ image of the object. Rod like cells respond to the faint light also but ______ cells do not. Some people lack conical cells responding to certain colours. These persons cannot recognize those colours or cannot distinguish between different ______. These persons are said to be ______.


Explain with a ray diagram the position, size, and nature of the various images formed by a convex lens.

An object is in between F1 and 2F1


Explain with a ray diagram the position, size, and nature of the various images formed by a convex lens.

Object at focus F1


Explain with a ray diagram the position, size, and nature of the various images formed by a convex lens.

Object between F1 and O


The image formed by a lens is always virtual, erect and smaller in size than an object kept at different positions in front of it. Identify the nature of the lens.


State whether the following statement is True or False

A concave lens can be used to produce an enlarged and erect image.


State whether the following statement is True or False

A convex lens always produces a real image.


Observe the figures given in Figure 15.1 carefully.

The given figures show the path of light through lenses of two different types, represented by rectangular boxes A and B. What is the nature of lenses A and B?


Two different types of lenses are placed on a sheet of newspaper. How will you identify them without touching them?


It was observed that when the distance between an object and a lens decreases, the size of the image increases. What is the nature of this lens? If you keep on decreasing the distance between the object and the lens, will you still be able to obtain the image on the screen? Explain.


A convex lens ‘A’ of focal length 20 cm and a concave lens ‘B’ of focal length 5 cm are kept along the same axis with a distance ‘d’ between them. If a parallel beam of light falling on ‘A’ leaves ‘B’ as a parallel beam, then the distance ‘d’ in cm will be ______.


A point object is placed at a distance of 60 cm from a convex lens of a focal length of 30 cm. If a plane mirror were put perpendicular to the principal axis of the lens and at a distance of 40 cm from it, the final image would be formed at a distance of:


A convex lens ‘A’ of focal length 20 cm and a concave lens ‘B’ of focal length 5 cm are kept along the same axis with a distance ‘d’ between them. If a parallel beam of light falling on ‘A’ leaves ‘B’ as a parallel beam, then the distance ‘d’ in cm will be ______


A point object is placed at a distance of 60 cm from a convex lens of focal length 30 cm. If a plane mirror were put perpendicular to the principal axis of the lens and at a distance of 40 cm from it, the final image would be formed at a distance of :


The power of a convex lens of focal length 25 cm is ______.


Draw the ray diagram of convex lens making image when object is at radius of curvature (2F1).

  1. An object is placed vertically at a distance of 20 cm from a convex lens. If the height of object is 5 cm and focal length of the lens is 10 cm, what will be its position, size and nature of image?
  2. Flow much bigger will the image be as compared to the object?

Distinguish between:

Concave Lens and Convex Lens


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