Ray Optics and Optical Instruments-Quiz-8

RAY OPTICS AND OPTICAL INSTRUMENTS-8 Quiz

Dear Readers,

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. With a concave mirror, an object is placed at a distance x_1 from the principal focus, on the principal axis. The image is formed at a distance x_2 from the principal focus. The focal length of the mirror is

•  x_1.x_2
•  (x_1+x_2)/2
•  √(x_1/x_2 )
•  √(x_1 x_2 )

Solution

Q2.Two lenses shown are illuminated by a beam of parallel light from the left. Lens B is then moved slowly toward lens A. The beam emerging from lens B is

•  Always diverging
•  Initially parallel and then diverging
•  Always parallel
•  Initially converging and then parallel

Solution

Q3.  A biconvex lens of focal length fforms a circular image of radius rof sun in focal plane. Then which option is correct?

•   πr^2∝f
•  πr²∝f^2
•  If lower half part is covered by black sheet, then area of the image is equal to πr² / 2
•  If fis doubled, intensity will increase

Solution
r=ftanθ Or r∝f ∴ πr^2∝f^2

Q4. Two thin symmetrical lenses of different nature and of different material have equal radii of curvature R=15 cm. The lenses are put close together and immersed in water (μ_w=4/3). The focal length of the system in water is 30 cm. The difference between refractive indices of the two lenses is

•  1/2
•  1/4
•  1/3
•  3/4

Solution

Q5. One of the refracting surfaces of a prism of angle 30° is silvered. A ray of light incident at angle of 60° retraces its path. The refractive index of the material of prism is

•  √2
•  √3
•  3/2
•  2

Solution

Q6. A spherical convex surface separates object and image spaces of refractive indices 1.0 and 4/3. If radius of curvature of the surface is 10 cm, find its power

•  3.5 dioptre
•  2.5 dioptre
• 25 dioptre
•  1.5 dioptre

Solution

Q7. A concave lens forms the image of an object such that the distance between the object and image is 10 cm and the magnification produced is 1/4. The focal length of the lens will be

•  8.6 cm
•  6.2 cm
•  10 cm
•  4.4 cm

Solution
Concave lens forms the virtual image of a real object. So, let u=-4x and v=-x Then, 3x=10 cm Or x=10/3cm ∴ u=-40/3 cm and v=-10/3 cm Subtracting in 1/f=(-3)/10+3/40 Or f=-40/9 Or f=-4.4 cm

Q8. Critical angle of glass is θ_1 and that of water is θ_2. The critical angle for water and glass surface would be (μ_g=3/2,μ_w=4/3)

•  Less than θ_2
•  TBetween θ_1 and θ_2
•  Greater than θ_2
•  Less than θ_1

Solution

Q9. A biconvex lens of focal length 15 cm is in front of a plane mirror. The distance between the lens and the mirror is 10 cm. A small object is kept at a distance of 30 cm from the lens. The final image is

•  Virtual and at a distance of 16 cm from the mirror
•  Real and at a distance of 16 cm from the mirror
•  Virtual and at a distance of 20 cm from the mirror
•  None of the abover

Solution

Q10. When an object is placed 15 cm from a lens, a virtual image is formed. Mark the correct statements

•  The lens may be convex or concave
•  If the lens is diverging, the image distance has to be less than 15 cm
•  If the lens is converging, then its focal length has to be greater than 15 cm
• All of the above

Solution
Both the lenses (convex or concave) form virtual image of a real extended object. In both the cases, image would be erect For convex lens, virtual image will form when object is in-between focus and optical center For concave lens, virtual image will form for any location of object, and corresponding image is lying between focus and optical center