## RAY OPTICS AND OPTICAL INSTRUMENTS-23 Quiz

JEE Advanced Physics Syllabus can be referred by the IIT aspirants to get a detailed list of all topics that are important in cracking the entrance examination. JEE Advanced syllabus for Physics has been designed in such a way that it offers very practical and application-based learning to further make it easier for students to understand every concept or topic by correlating it with day-to-day experiences. In comparison to the other two subjects, the syllabus of JEE Advanced for physics is developed in such a way so as to test the deep understanding and application of concepts.

Q1. Statement 1: By increasing the diameter of the objective of telescope, we can increase its range
Statement 2: The range of a telescope tells us how far away a star of some standard brightness can be spotted by telescope
•   Statement 1 is True, Statement 2 is True; Statement 2 is correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is True; Statement 2 is not correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is False
•   Statement 1 is False, Statement 2 is True
Solution
(b)The light gathering power (or brightness) of a telescope ∝(diameter)^2. So by increasing the objective diameter even far off stars may produce images of optimum brightness

Q2.Statement 1: If the angles of the base of the prism are equal, then in the position of minimum deviation, the refracted ray will pass parallel to the base of prism
Statement 2: In the case of minimum deviation, the angle of incidence is equal to the angle of emergence
•   Statement 1 is True, Statement 2 is True; Statement 2 is correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is True; Statement 2 is not correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is False
•   Statement 1 is False, Statement 2 is True
Solution
(a) In case of minimum deviation of a prism ∠i=∠e
so ∠r_1=∠r_2

Q3.  Statement 1: The polar caps of earth are cold in comparison to equatorial plane
Statement 2: The radiation absorbed by polar caps is less than the radiation absorbed by equatorial plane
•   Statement 1 is True, Statement 2 is True; Statement 2 is correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is True; Statement 2 is not correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is False
•   Statement 1 is False, Statement 2 is True
Solution
(c) Polar caps receives almost the same amount of radiation as the equatorial plane. For the polar caps angle between sun rays and normal (to polar caps) tends to 90°. As per Lambert’s cosine law, E∝cos⁡Î¸, therefore E is zero. For the equatorial plane, Î¸=0°, therefore E is maximum. Hence polar caps of earth are so cold. (where E is radiation received)

Q4. Statement 1: The fluorescent tube is considered better than an electric bulb
Statement 2: Efficiency of fluorescent tube is more than the efficiency of electric bulb
•   Statement 1 is True, Statement 2 is True; Statement 2 is correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is True; Statement 2 is not correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is False
•   Statement 1 is False, Statement 2 is True
Solution
(a) The efficiency of fluorescent tube is about 50 lumen/watt,
whereas efficiency of electric bulb is about 12 lumen/watt.
Thus for same amount of electric energy consumed, the tube gives nearly 4 times more light than the filament bulb

Q5. Statement 1: The formula connecting u,v and f for a spherical mirror is valid only for mirrors whose sizes are very small compared to their radii of curvature.
Statement 2: Laws of reflection are strictly valid for plane surfaces, but not for large spherical surfaces.
•   Statement 1 is True, Statement 2 is True; Statement 2 is correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is True; Statement 2 is not correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is False
•   Statement 1 is False, Statement 2 is True
Solution
(c) Laws reflection can be applied to any type of surface

Q6. Statement 1: For the sensitivity of a camera, its aperture should be reduced
Statement 2: Smaller the aperture , image focusing is also sharp
•   Statement 1 is True, Statement 2 is True; Statement 2 is correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is True; Statement 2 is not correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is False
•   Statement 1 is False, Statement 2 is True
Solution
(c)
Very large apertures gives blurred images because of aberrations.
By reducing the aperture the clear image is obtained and thus the sensitivity of camera increases.
Also the focussing of object at different distance is achieved by slightly altering the separation of the lens from the film

Q7. Statement 1: The focal length of lens does not change when red light is replaced by blue light
Statement 2: The focal length of lens does not depends on colour of light used
•   Statement 1 is True, Statement 2 is True; Statement 2 is correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is True; Statement 2 is not correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is False
•   Statement 1 is False, Statement 2 is True
Solution
(d)Focal length of the lens depends upon it’s refractive index as 1/f∝(Î¼-1)
Since Î¼_b>Î¼_r so f_b less than f_r
Therefore, the focal length of a lens decreases when red light is replaced by blue light

Q8. Statement 1: Owls can move freely during night
Statement 2: They have large number of rods on their retina
•   Statement 1 is True, Statement 2 is True; Statement 2 is correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is True; Statement 2 is not correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is False
•   Statement 1 is False, Statement 2 is True
Solution
Owls can move freely during night, because they have large number of cones on their retina which help them to see in night

Q9. Statement 1: A virtual image can be photographed
Statement 2: Only a real image can be formed on a screen
•   Statement 1 is True, Statement 2 is True; Statement 2 is correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is True; Statement 2 is not correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is False
•   Statement 1 is False, Statement 2 is True
Solution
The rays of light are diverging out from a virtual image. These can be easily converged onto the film of a concave lens by convergent action of its lens

Q10. Statement 1: If objective and eye lenses of a microscope are interchanged then it can work as telescope
Statement 2: The objective of telescope has small focal length

•   Statement 1 is True, Statement 2 is True; Statement 2 is correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is True; Statement 2 is not correct explanation for Statement 1
•   Statement 1 is True, Statement 2 is False
•   Statement 1 is False, Statement 2 is True
Solution
We cannot interchange the objective and eye lens of a microscope to make a telescope. The reason is that the focal length of lenses in microscope are very small, of the order of mm or a few cm and the difference (f_o-f_e) is very small, while the telescope objective have a very large focal length as compared to eye lens of microscope

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