Chapter 23

A convex lens forms a real image of a point object placed on its principal axis. If the upper half of the lens is painted black, (a) the image will be shifted upward (b) the image will be shifted downward (c) the intensity of the image will decrease (d) the image will not be shifted

The magnifying power of an astronomical telescope is 10 and the focal length of its eye-piece is \(20 \mathrm{~cm}\). The focal length of its objective will be (a) \(200 \mathrm{~cm}\) (b) \(2 \mathrm{~cm}\) (c) \(0.5 \mathrm{~cm}\) (d) \(0.5 \times 10^{-2} \mathrm{~cm}\)

A magnifying glass is used, as the object to be viewed can be brougth closer to the eye than the normal near point. This results in |NCERT Exemplar] (al a larger angle to be subtended by the object at the eye and hence viewed in greater detail (b) the formation of a virtual erect image (c) increase in the field of view (d) infinite magnification at the near point

A ray of light incident at an angle \(\theta\) on a refracting face of a prism emerges from the other face normally. If the angle of the prism is \(5^{\circ}\) and the prism is made of a material of refractive index \(1.5\), the angle of incidence is [NCFRT Exemplar] (a) \(7.5^{\circ}\) (b) \(5^{*}\) (c) \(15^{*}\) [d) \(2.5^{*}\)

An astronomical refractive telescope has an objective of focal length \(20 \mathrm{~m}\) and an eyepiece of focal length \(\begin{array}{ll}2 \mathrm{~cm} . & \text { INCERT Exemplar] }\end{array}\) (a) The length of the telescope tube is \(20.02 \mathrm{~m}\) (b) The magnification is 1000 (c) The image formed is imverted (d) An obdective of a larger aperture will increase the brigthtness and reduce chromatic aberration of the image

The refractive index of a prism for a monochromatic wave is \(\sqrt{2}\) and its refracting angle is \(60^{\circ}\). For minimum deviation, the angle of incidence will be (a) \(3 \overline{0^{\circ}}\) (b) \(45^{*}\) (c) \(60^{\circ}\) (d) \(75^{\circ}\)

It is desired to make a converging achromatic combination of mean focal length \(50 \mathrm{~cm}\) by using two lenses of materials \(A\) and \(B\). If the dispersive powers of \(A\) and \(B\) are in ratio \(1: 2\), the focal lengths of the convex and the concave lenses are respectively (a) \(25 \mathrm{~cm}\) and \(50 \mathrm{~cm}\) (b) \(50 \mathrm{~cm}\) and \(25 \mathrm{~cm}\) (c) \(50 \mathrm{~cm}\) and \(100 \mathrm{~cm}\) (d) \(100 \mathrm{~cm}\) and \(50 \mathrm{~cm}\)

Total internal reflection is the phenomenon of reflection of light into denser medium at the interface of denser medium with a rarer medium. Light must. travel from denser to rarer and angle incidence denser medium must be greater than critical angle (C) for the pair of media in contact. We can show that $$ \mu=\frac{1}{\sin C} $$ Critical angle for water air interface is \(48.6^{\circ}\). What is the refractive index of water? (a) (b) \(3 / 2\) (c) \(4 / 3\) (d) \(3 / 4\)

The refractive index of the material of a prism is \(\sqrt{2}\) and the angle of prism is \(30^{\circ} .\) One of its refracting faces is polished, the incident beam of light will retrace back for angle of incidence (a) \(0^{\circ}\) (b) \(45^{*}\) (c) \(60^{\circ}\) (d) \(90^{*}\)

Total internal reflection is the phenomenon of reflection of light into denser medium at the interface of denser medium with a rarer medium. Light must. travel from denser to rarer and angle incidence denser medium must be greater than critical angle (C) for the pair of media in contact. We can show that $$ \mu=\frac{1}{\sin C} $$ Critical angle for glass air-interface where refractive index \(\mu\) of glass is \(3 / 2\), is (a) \(41.8^{*}\) (b) \(60^{*}\) (c) \(30^{*}\) (d) \(44.3^{*}\)

The cross-section of a glass prism has the form of an isoceles triangle. One of the refracting faces is silvered. A ray of light falls normally on the other refracting face. After being reflected twice, it emerges through the base of the prism perpendicular to it. The angles of the prism are (a) \(54^{*}, 54^{*}, 72^{*}\) (b) \(72^{*}, 72^{*}, 36^{*}\) (c) \(45^{\circ}, 45^{\prime \prime}, 90^{\circ}\) (d) \(57^{\prime}, 57^{\circ}, 76^{\circ}\)

The maximum refractive index of a prism which permits the passage of light through it, when the refracting angle of the prism is \(90^{\circ}\), is (a) \(\sqrt{3}\) (b) \(\sqrt{2}\) (c) \(\frac{\sqrt{3}}{2}\) (d) \(\frac{3}{2}\)

Total internal reflection is the phenomenon of reflection of light into denser medium at the interface of denser medium with a rarer medium. Light must. travel from denser to rarer and angle incidence denser medium must be greater than critical angle (C) for the pair of media in contact. We can show that $$ \mu=\frac{1}{\sin C} $$ A point source of light is held at a depth \(h\) below the surface of water. If \(C\) is critical angle of air water interface, the diameter of cirele of light coming from water surface would be (a) \(2 \underline{h} \tan C\) (b) \(h \tan C\) (c) \(h \sin C\) (d) \(h / \sin C\)

The following statements carefully to mark correct option are options given below (a) Statement 1 is true, Statement 2 is true. Statement 2 is a correct explanation for Statement 1 (b) Statement 1 is true, Statement 2 is true, Statement 2 is not a correct explanation for Statement 1 (c) Statement 1 is true, Statement 2 is false (d) Statement 1 is false, Statement 2 is true Statement 1 The formula connecting \(u, v\) and \(f_{4}\) 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 surface, but not for large spherical surfaces.

Assertion-Reason type. Each of these contains two Statements: Statement I (Assertion), Statement II (Reason). Each of these questions also has four alternative choice, only one of which is correct. You have to select the correct choices from the codes \((a)\), (b) \((c)\) and \((d)\) given below (a) If both Assertion and Reason are true and the Reason is correct explanation of the Assertion (b) If both Assertion and Reason are true but Reason is not correct explanation of the Assertion (c) If Assertion is true but Reason is false (d) If Assertion is false but the Reason is true Assertion A concave mirror and convex lens both have the same focal length in air. When they are submerged in water, they will still have the same focal length. Reason The refractive index of water is greater than the refractive index of air.

Assertion-Reason type. Each of these contains two Statements: Statement I (Assertion), Statement II (Reason). Each of these questions also has four alternative choice, only one of which is correct. You have to select the correct choices from the codes \((a)\), (b) \((c)\) and \((d)\) given below (a) If both Assertion and Reason are true and the Reason is correct explanation of the Assertion (b) If both Assertion and Reason are true but Reason is not correct explanation of the Assertion (c) If Assertion is true but Reason is false (d) If Assertion is false but the Reason is true Assertion The focal length of the objective of the telescope is larger than that of eyepiece. Reason The resolving power of telescope increases when the aperture of objective is small.

Assertion-Reason type. Each of these contains two Statements: Statement I (Assertion), Statement II (Reason). Each of these questions also has four alternative choice, only one of which is correct. You have to select the correct choices from the codes \((a)\), (b) \((c)\) and \((d)\) given below (a) If both Assertion and Reason are true and the Reason is correct explanation of the Assertion (b) If both Assertion and Reason are true but Reason is not correct explanation of the Assertion (c) If Assertion is true but Reason is false (d) If Assertion is false but the Reason is true Assertion A short sighted person cannot see objects clearly when placed beyond \(50 \mathrm{~cm}\). He should use a concave lens of power \(2 \mathrm{D}\). Reason Concave lens should form image of an object. at infinity placed at a distance of \(50 \mathrm{~cm}\).

Assertion-Reason type. Each of these contains two Statements: Statement I (Assertion), Statement II (Reason). Each of these questions also has four alternative choice, only one of which is correct. You have to select the correct choices from the codes \((a)\), (b) \((c)\) and \((d)\) given below (a) If both Assertion and Reason are true and the Reason is correct explanation of the Assertion (b) If both Assertion and Reason are true but Reason is not correct explanation of the Assertion (c) If Assertion is true but Reason is false (d) If Assertion is false but the Reason is true Assertion The refractive index of diamond is \(\sqrt{6}\) and that of liquid is \(\sqrt{3}\). If the light travels from diamond to the liquid, it will initially reflected when the angle of incidence is \(30^{\circ}\). Reason \(\mu=\frac{1}{\sin C}\) where \(\mu\) is the refractive index of diamond with respect to liquid.

Assertion-Reason type. Each of these contains two Statements: Statement I (Assertion), Statement II (Reason). Each of these questions also has four alternative choice, only one of which is correct. You have to select the correct choices from the codes \((a)\), (b) \((c)\) and \((d)\) given below (a) If both Assertion and Reason are true and the Reason is correct explanation of the Assertion (b) If both Assertion and Reason are true but Reason is not correct explanation of the Assertion (c) If Assertion is true but Reason is false (d) If Assertion is false but the Reason is true Assertion The colour of the green flower seen through red glass appears to be dark. . Reason Red glass transmits only red light.

Assertion-Reason type. Each of these contains two Statements: Statement I (Assertion), Statement II (Reason). Each of these questions also has four alternative choice, only one of which is correct. You have to select the correct choices from the codes \((a)\), (b) \((c)\) and \((d)\) given below (a) If both Assertion and Reason are true and the Reason is correct explanation of the Assertion (b) If both Assertion and Reason are true but Reason is not correct explanation of the Assertion (c) If Assertion is true but Reason is false (d) If Assertion is false but the Reason is true Assertion The stars twinkle while the planets is do not. Reason The stars are much brgger in size than planets.

Assertion-Reason type. Each of these contains two Statements: Statement I (Assertion), Statement II (Reason). Each of these questions also has four alternative choice, only one of which is correct. You have to select the correct choices from the codes \((a)\), (b) \((c)\) and \((d)\) given below (a) If both Assertion and Reason are true and the Reason is correct explanation of the Assertion (b) If both Assertion and Reason are true but Reason is not correct explanation of the Assertion (c) If Assertion is true but Reason is false (d) If Assertion is false but the Reason is true Assertion Owls can move freely during night. Reason They have large number of rods on their retina.

Assertion-Reason type. Each of these contains two Statements: Statement I (Assertion), Statement II (Reason). Each of these questions also has four alternative choice, only one of which is correct. You have to select the correct choices from the codes \((a)\), (b) \((c)\) and \((d)\) given below (a) If both Assertion and Reason are true and the Reason is correct explanation of the Assertion (b) If both Assertion and Reason are true but Reason is not correct explanation of the Assertion (c) If Assertion is true but Reason is false (d) If Assertion is false but the Reason is true Assertion The focal length of the mirror is \(f\) and distance of the object from the focus is \(u\), the magnification of the mirror is \(f / u\). .Reason Magnification \(=\frac{\text { Size of image }}{\text { Size of object }}\)

Let the \(x z\)-plane be the boundary between two transparent media. Medium 1 in \(z \geq 0\) has a refractive index of \(\sqrt{2}\) and medium 2 with \(z<0\) has a refractive index \(\sqrt{3} .\) A ray of light in medium 1 given by the vector \(\mathbf{A}=6 \sqrt{3} \hat{\mathbf{i}}+8 \sqrt{3} \hat{\mathbf{j}}-10 \hat{\mathbf{k}}\) is incident on the plane of separation. The angle of refraction in medium 2 is (a) \(45^{*}\) (b) \(60^{\circ}\) (c) 75 (d) \(30^{*}\)

\mathrm{\\{} T h i s ~ q u e s t i o n ~ h a s ~ a ~ p a r a g r a p h ~ f o l l o w e d ~ b y ~ t w o ~ statements, Statement 1 and Statement 2. Of the given four alternatives after the statements, choose the one that describes the statements. A thin air film is formed by putting the convex surface of a plano-convex lens over a plane glass plate. With monochromatie light, this film gives an interference pattern due to light reflected from the top (convex) surface and he bottom (glass plate) surface of the film. Statement 1 When light reflects from the air-glass plate interface, the reflected wave suffers a phase change of \(\pi\). Statement 2 The centre of the interference pattern is dark. (a) Statement 1 is true, Statement 2 is true, Statement 2 is the correct explanation of Statement \(\mathbb{I}\). (b) Statement 1 is true, Statement 2 is true, Statement 2 is not the correct explanation of Statement \(1 .\) (c) Statement 1 is false, Statement 2 is true. (d) Statement 1 is true, Statement 2 is false.

A car is fitted with a convex side-view mirror of focal length \(20 \mathrm{~cm}\). A second car \(2.8 \mathrm{~m}\) behind the first car is overtaking the first car at a relative speed of \(15 \mathrm{~m} / \mathrm{s}\). The speed of the image of he second car as seen in the mirror of the first one is (a) \(\frac{1}{15} \mathrm{~m} / \mathrm{s}\) (b) \(10 \mathrm{~m} / \mathrm{s}\) (c) \(15 \mathrm{~m} / \mathrm{s}\) (d) \(\frac{1}{10} \mathrm{~m} / \mathrm{s}\)

Based on the following paragraph. An initially parallel cylindrical beam travels in a medium of refractive index, \(\mu(I)=\mu_{e}+\mu_{2} I\), where \(\mu_{0}\) and \(\mu_{2}\) are positive constants and \(I\) is the intensity of the light beam. The intensity of the beam is decreasing with increasing radius. The speed of light in the medium is \(\quad\) [AIFEE 2010] (a) minimum on the axis of the beam (b) the same everywhere in the beam (c) directly proportional to the intensity (d) maximum on the axis of the beam

An object \(2.4 \mathrm{~m}\) infront of a lens forms a sharp image on a film \(12 \mathrm{~cm}\) behind the lens. A glass plate \(1 \mathrm{~cm}\) thick, of refractive index \(1.50\) is interposed between lens and film with its plane faces parallel to film. At what distance (from lens) should object shifted to be in sharp focus on film? [AIFEE 2012] (a) \(7.2\) (b) \(2.4\) (c) \(3.2\) [d] 5.6

A thin lens of glass \((\mu=1.5)\) of focal length \(+10 \mathrm{~cm}\) is immersed in water \((\mu=1.33)\). The new focal length is [AIFEE 2009] (a) \(12 \mathrm{~cm}\) (b) \(20 \mathrm{~cm}\) (c) \(40 \mathrm{~cm}\) (d) \(40 \mathrm{~cm}\)

A ray \(O P\) of monochromatic light is incident on the face \(A B\) of prism \(A B C D\) near vertex. \(B\) at an incident angle of \(60^{\circ}\) (see figure). If the refractive index of the material of the prism is \(\sqrt{3}\), which of the following is (are) correet? [IIT JEF 2010] (a) The ray gets totally internally reflected at face \(\mathrm{CD}\) (b) The ray comes out through face \(A D\) (c) The angle between the incident ray and the emergent ray is \(90^{\circ}\) (d) The angle between the incident ray and the emergent ray is \(120^{\circ}\)

The distance between an object and a divergent lens is \(m\) times the focal length of the lens. The linear magnification produced by the lens is (a) \(\bar{m}\) (b) \(1 / m\) (c) \((m+1)\) (d) \(\frac{1}{m+1}\)