Geometrical Optics Questions and Answers

A ray of light enters at grazing angle of incidence into an assembly by three isoscl right angled prisms having refractive indices 2 x and 3 3 If finally emerge light ray also emerges at grazing angle then x is H H H3

A biconvex thin lens is prepared from glass 1 5 the two bounding surfaces having equal radii of 25 cm each One of the surfaces is silvered from outside to make it reflecting An object is placed before this lens at distance 1 cm so that the image is formed on the object itself The value of 20 is Lens is placed in air u 1 5 C 25cm B 25cm C

Light passes from air into water How does the angle of incidence compare to the angle Incidence angle Refraction angle Incidence angle Refraction angle Incidence angle Refraction angle

of 10cm Find the total momentum delivered during 10 minutes time span 6 A thin double convex lens of focal length f is broken into two equal halves at the axis The two halves are combined as shown in figure What is the focal length of combination in ii Q ii

58 Suppose you have three concave mirrors A B and C of focal lengths 10 cm 15 cm and 20 cm or each concave mirror you perform the experiment of image formation for three values of object listance of 10 cm 20 cm and 30 cm Giving reason answer the following A For the three object distances identify the mirror mirrors which will form an image of magnification 1

In Young s double slit experiment if monochromatic light is replaced by white light 1 All bright fringes become white 2 All bright fringes have colours between violet and red 3 Only the central fringe is white all other fringes are coloured 4 No fringes are observed

Example 9 7 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 Solution The refractive index of the liquid must be equal to 1 47 in order to make the lens disappear This means n n This gives 1 f 0 or f The lens in the liquid will act like a plane sheet of glass No the liquid

1 A coin 3 00 cm in diameter is embedded in a solid glass sphere of radius 40 0 cm The index of refraction of the sphere is 1 50 and the coin is at 30 0 cm from the surface of the sphere as shown in the figure below i Find the position of the image ii What is the magnification of the image 3 U coin CALASS 400m x 30cm M 1 S

29 Diameter of a plano convex lens is 6 cm and its thickness at the centre is 3 mm Then the focal length of the lens if the speed of light in the material of lens is 2 x 108 m s 1 7 5 cm 3 45 cm 2 15 cm 4 30 cm

A wire of length L and cross sectional area A made of a material of Young s modulus Y is pulled with a constant force F on a rough horizontal surface havin coefficient of friction as shown in fig Then A extension in the wire is B extension in the wire is FC YA FC 2YA F C tension in the rod at the middle point of the rod is 2 F mg

A thin biconvex lens of refractive index 3 2 is placed on a horizontal plane mirror as shown in the figure The space between the lens and the mirror is then filled with water of refractive index 4 3 It is found that when a point object is placed 15 cm above the lens on its principle axis the object coincides with its own image On repeating with another liquid the object and the image again coincide at a distance 25 cm from the lens Calculate the refractive index of the liquid

A convex lens of focal length f is placed somewhere in between an object and a screen The distance between the object and the screen is x If the numerical value of the magnification produced by the lens is m then the focal length of the lens is 1 2 3 4 mx m 1 mx m 1 m 1 m X m 1 X

A object is placed at a distance of 1 5 m from screen and a convex lens is placed in betwee them which produces 4 times magnified imag on the screen Find the focal length and th position of lens from the object 1 f 0 24 m 0 6 m 2 f 0 375 m a 0 75 m 3 f 0 24 m 0 3 m 4 f 0 375 m 0 3 m

An object is placed closer to a converging lens than its focal length Can the image be projected onto a screen no because it will be a virtual image O yes because it will be a virtual image yes because it will be a real image no because it will be a real image

A phone is placed at a distance of twice the focal length from a lens What type of image will be produced on the opposite side of the lens that can be projected onto a screen virtual Oreal optical

4 A steel wire is coaxially embedded in a glass tube external diameter of which is much greater than that of the wire Refractive index of the glass is 4 3 If diameter of the steel wire appears 8 3 mm when looked into the glass tube through its curved surface find the actual diameter of the 2 mm steel wire