Define the magnifying power of a compound microscope when the final image is formed at infinity. Why must both the objective and the eyepiece of a compound microscope has short focal lengths? Explain.
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2 Marks Questions
93 Q→023 Marks Question
108 Q→031 Marks Question
44 Q→044 Marks Questions
23 Q→05M.C.Q (1 Marks)
176 Q→06Assertion (A) & Reason (B) MCQ
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118 Q→Sample Questions
Ray Optics and Optical Instruments questions
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A person looking at a person wearing a shirt with a pattern comprising vertical and horizontal lines is able to see the vertical lines more distinctly than the horizontal ones. What is this defect due to? How is such a defect of vision corrected?
Answer the following question:
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., the retina) of our eye. Is there a contradiction?
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., the retina) of our eye. Is there a contradiction?
Does short-sightedness (myopia) or long-sightedness (hypermetropia) imply necessarily that the eye has partially lost its ability of accommodation? If not, what might cause these defects of vision?
Answer the following question:
In viewing through a magnifying glass, one usually positions one’s eyes very close to the lens. Does angular magnification change if the eye is moved back?
In viewing through a magnifying glass, one usually positions one’s eyes very close to the lens. Does angular magnification change if the eye is moved back?
- A ray of light incident on face AB of an equilateral glass prism, shows minimum deviation of 30°. Calculate the speed of light through the prism.
- Find the angle of incidence at face AB so that the emergent ray grazes along the face AC.
Double - convex lenses are to be manufactured from a glass of refractive index 1.55, with both faces of the same radius of curvature. What is the radius of curvature required if the focal length is to be 20cm?
If this telescope is used to view a 100 m tall tower 3 km away, what is the height of the image of the tower formed by the objective lens?
What should be the distance between the object in Exercise 9.30 and the magnifying glass if the virtual image of each square in the figure is to have an area of 6.25 mm2. Would you be able to see the squares distinctly with your eyes very close to the magnifier?
A small telescope has an objective lens of focal length 140 cm and an eyepiece of focal length 5.0 cm. What is the magnifying power of the telescope for viewing distant objects when,
- the telescope is in normal adjustment (i.e., when the final image is at infinity)?
- the final image is formed at the least distance of distinct vision (25 cm)?
What is the height of the final image of the tower if it is formed at 25cm?
What is the magnification in this case?
For the telescope described in, what is the separation between the objective lens and the eyepiece?
A magician during a show makes a glass lens with $n=1.47$ disappear in a trough of liquid. What is the refractive index of the liquid? Could the liquid be water?
View full solution →Light from a point source in air falls on a spherical glass surface ( $n=1.5$ and radius of curvature $=20 cm )$. The distance of the light source from the glass surface is $100 cm$. At what position the image is formed?
View full solution →- A ray of light is incident normally on the face AB of a right-angled glass prism of refractive index $_{a}\mu_{g} =1.5$The prism is partly immersed in a liquid of unknown refractive index. Find the value of refractive index of the liquid so that the ray grazes along the face BC after refraction through the prism.
- Trace the path of the rays if it were incident normally on the face AC.
- A point-object is placed on the principal axis of a convex spherical surface of radius of curvature R, which separates the two media of refractive indices n 1 and n 2 (n 2 > n 1). Draw the ray diagram and deduce the relation between the distance of the object (u),distance of the image (v) and the radius of curvature (R) for refraction to take place at the convex spherical surface from rarer to denser medium.
- Use the above relation to obtain the condition on the position of the object and the radius of curvature in terms of n1 and n2 when the real image is formed.
An object AB is kept in front of a concave mirror as shown in the figure.
- Complete the ray diagram showing the image formation of the object.
- How will the position and intensity of the image be affected if the lower half of the mirror's reflecting surface is painted black?
- A mobile phone lies along the principal axis of a concave mirror. Show, with the help of a suitable diagram, the formation of its image. Explain why magnification is not uniform.
- Suppose the lower half of the concave mirror's reflecting surface is covered with an opaque material. What effect this will have on the image of the object? Explain.
A lady cannot see objects closer than 40cm from the left eye and closer than 100cm from the right eye. While on a mountaineering trip, she is lost from her team. She tries to make an astronomical telscope from her reading glasses to look for her teammates.
- Which glass should she use as the eyepiece?
- What magnification can she get with relaxed eye?
Two unequal resistors are connected in series across a battery. Then the:
- APotential difference across each resistor is the same.
- BCurrent in the smaller resistor is larger.
- CPotential difference across the bigger resistor is greater.
- DPower dissipated in both resistors is the same.
The focal length of the objective of a compound microscope is:
- AGreater than the focal length of eyepiece.
- BLesser than the focal length of eyepiece.
- CEqual to the focal length of eyepiece.
- DEqual to the length of its tube.
A biconvex lens of glass having refractive index 1.47 is immersed in a liquid. It becomes invisible and behaves as a plane glass plate. The refractive index of the liquid is:
- A1.47
- B1.62
- C1.33
- D1.51
For a glass prism, the angle of minimum deviation will be smallest for the light of:
- ARed colour.
- BBlue colour.
- CYellow colour.
- DGreen colour.
The resistance of a metal wire increases with increasing temperature on account of:
- ADecrease in free electron density.
- BDecrease in relaxation time.
- CIncrease in mean free path.
- DIncrease in the mass of electron.
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Reason: Optical fibres are based on phenomena of total internal reflection.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false and R is also false.
Reason: Optical fibres are based on phenomena of total internal reflection.
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Reason: For an equiconvex lens, radius of curvature of both the faces is same.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false and R is also false.
Reason: For an equiconvex lens, radius of curvature of both the faces is same.
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Reason: The distance between an object and its real image is minimum when its magnification is two.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false and R is also false.
Reason: The distance between an object and its real image is minimum when its magnification is two.
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Reason: Air is rarer than glass.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false and R is also false.
Reason: Air is rarer than glass.
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Reason: There is no loss of intensity in total internal reflection.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false and R is also false.
Reason: There is no loss of intensity in total internal reflection.
A card sheet divided into squares each of size 1 mm2 is being viewed at a distance of 9 cm through a magnifying glass (a converging lens of focal length 9 cm) held close to the eye.
- What is the magnification produced by the lens? How much is the area of each square in the virtual image?
- What is the angular magnification (magnifying power) of the lens?
- Is the magnification in (a) equal to the magnifying power in (b)? Explain.
What is the focal length of a convex lens of focal length 30cm in contact with a concave lens of focal length 20 cm? Is the system a converging or a diverging lens? Ignore thickness of the lenses.
Determine the ‘effective focal length’ of the combination of the two lenses in if they are placed 8.0 cm apart with their principal axes coincident. Does the answer depend on which side of the combination a beam of parallel light is incident? Is the notion of effective focal length of this system useful at all.
A Cassegrain telescope uses two mirrors. Such a telescope is built with the mirrors 20 mm apart. If the radius of curvature of the large mirror is 220 mm and the small mirror is 140 mm, where will the final image of an object at infinity be?
An angular magnification (magnifying power) of 30X is desired using an objective of focal length 1.25 cm and an eyepiece of focal length 5 cm. How will you set up the compound microscope?
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