LOADING . . .
જવાબ : negative
જવાબ : Magnification
જવાબ : concave
જવાબ : real
જવાબ : reflection
જવાબ : reflection
જવાબ : plane or convex mirror
જવાબ : concave
જવાબ : virtual
જવાબ : concave
જવાબ : dioptre
જવાબ : reciprocal
જવાબ : 3 x 108 m/s
જવાબ : dispersion
જવાબ : Power of lens (P) = 1/f P = 1.5D f = 1/1.5 = 10/15 = 0.66 m A convex lens has a positive focal length. Therefore, it is a convex lens or a converging lens.
જવાબ : Power of lens (P) = 1/f P = 2D f = 1/2 = 0.5 m A concave lens has a negative focal length. Therefore, it is a concave lens
જવાબ : The positive sign means an image formed by a plane mirror is virtual and erect. Since the magnification is 1 it means that the size of the image is equal to the size of the object.
જવાબ : Yes, it will produce a complete image of the object, as shown in the figure. This can be verified experimentally by observing the image of a distant object like a tree on a screen when the lower half of the lens is covered with a black paper. However, the intensity or brightness of the image will reduce.
જવાબ : (a) Concave Mirror: Because concave mirrors can produce a powerful parallel beam of light when the light source is placed at their principal focus. (b) Convex Mirror: Because of its largest field of view. (c) Concave Mirror: Because it concentrates the parallel rays of the sun at a principal focus.
જવાબ : Range of the distance of the object = 0 to 15 cm from the pole of the mirror. Nature of the image = virtual, erect, and larger than the object.
જવાબ : Focal length of concave lens (f) = 2 m Power of lens (P) = 1/f = 1/ (2) = 0.5D
જવાબ : Dioptre is the SI unit of power of lens is denoted by the letter D. 1 dioptre can be defined as the power of a lens of focal length 1 metre.
જવાબ : Diamond has a refractive index of 2.42 which means that the speed of light in diamond will reduce by a factor of 2.42 as compared to its speed in the air. In other words, the speed of light in diamond is 1/2.42 times the speed of light in vacuum.
જવાબ : Refractive index of a medium (nm) = Speed of light in vacuum/Speed of light in the medium Speed of light in vacuum (c) = 3 × 108 m/s Refractive index of glass (ng) = 1.50 Speed of light in the glass (v) = Speed of light in vacuum/ Refractive index of glass = c/ng =3 × 108/1.50 = 2x 108 ms1.
જવાબ : The light ray bends towards the normal. When a light ray enters from an optically rarer medium (which has low refractive index) to an optically denser medium (which has a high refractive index), its speed slows down and bends towards the normal. As water is optically denser than air, a ray of light entering from air into water will bend towards the normal.
જવાબ : Radius of curvature (R) = 20 cm Radius of curvature of the spherical mirror = 2 × Focal length (f) R = 2f f= R/2 = 20 / 2 = 10 Therefore, the focal length of the spherical mirror is 10 cm.
જવાબ : Convex mirror is preferred as a rearview mirror in cars and vehicles as it gives a wider field of view, which helps the driver to see most of the traffic behind him. Convex mirrors always form an erect, virtual, and diminished image of the objects placed in front of it.
જવાબ : Radius of curvature (R) = 32 cm Radius of curvature = 2 × Focal length (f) R= 2f f = R/2 = 32/2 = 16 Therefore, the focal length of the given convex mirror is 16 cm.
જવાબ : Magnification produced by a spherical mirror:
જવાબ : Light rays that are parallel to the principal axis of a concave mirror converge at a specific point on its principal axis after reflecting from the mirror. This point is called the principal focus of the concave mirror.
જવાબ : The distance between the pole and principal focus of a spherical mirror is called focal length of the spherical mirror.
જવાબ : A point on the principal axis, where the rays of light parallel to the principal axis meet after reflection from the concave mirror is called the principal focus of the concave mirror.
જવાબ : A point on the principal axis, where rays of light parallel to the principal axis appear to meet after reflecting from the convex mirror.
જવાબ : The process of returning or bouncing back the light to the same medium after striking the surface is called reflection of light.
જવાબ : A surface which reflects the light is called reflector.
જવાબ :
જવાબ : For normal incidence, ∠i = 0. Therefore, according to law of reflection ∠r = ∠i = 0.
જવાબ : When rays of light from an object actually meet at a point after refraction, then image formed is real.
જવાબ : Image is virtual, erect and of the same size as that of the object.
જવાબ : When rays of light from an object do not meet at a point but appears to meet at a point, then image formed is virtual.
જવાબ : The centre of a hollow sphere of which the spherical mirror forms a part is called the centre of curvature of the spherical mirror.
જવાબ : The radius of a hollow sphere of which the spherical mirror forms a part is called radius of curvature of the spherical mirror.
જવાબ : The part of spherical mirror exposed to the incident light is called the aperture of the spherical mirror.
જવાબ : The mid point of the spherical mirror is called the pole of spherical mirror.
જવાબ : The line joining the centre of curvature and pole of the spherical mirror and extended on either side is called the principal axis of the spherical mirror.
જવાબ : The mirror that can give an erect and enlarged image of an object is Concave Mirror.
Object distance (u) = – 10 cm v = 3 × ( 10) = – 30 cm Therefore, the negative sign indicates that an inverted image is formed in front of the given concave mirror at a distance of 30 cm.જવાબ : The position of the image should be at 2F since the image is the real and same size.
It is given that the image of the needle is formed at a distance of 50 cm from the convex lens. Therefore, the needle is placed in front of the lens at a distance of 50 cm. Object distance (u) = – 50 cm Image distance, (v) = 50 cm Focal length = f According to the lens formula,જવાબ : Height of the Object, h_{0} = 5 cm
Distance of the object from converging lens, u = 25 cm Focal length of a converging lens, f = 10 cm Using lens formula, Thus, the image is inverted and formed at a distance of 16.7 cm behind the lens and measures 3.3 cm. The ray diagram is shown below.જવાબ : Focal length of convex mirror (f) = +15 cm
Object distance (u) = – 10 cm According to the mirror formula, The image is located at a distance of 6 cm from the mirror on the other side of the mirror. The positive and a value of less than 1 of magnification indicates that the image formed is virtual and erect and diminished.જવાબ : Magnification produced by a mirror is given by the relation
The magnification produced by a plane mirror is +1. It shows that the image formed by the plane mirror is of the same size as that of the object. The positive sign shows that the image formed is virtual and erect.જવાબ : Range of object distance = 0 cm to15 cm
A concave mirror gives an erect image when an object is placed between its pole (P) and the principal focus (F). Hence, to obtain an erect image of an object from a concave mirror of focal length 15 cm, the object must be placed anywhere between the pole and the focus. The image formed will be virtual, erect, and magnified in nature, as shown in the given figure.જવાબ : Focal length of concave lens, f = 2 m
Here, negative sign arises due to the divergent nature of concaveજવાબ : When an object is placed at the centre of curvature, 2F_{1}, of a convex lens, its image is formed at the centre of curvature, 2F_{2}, on the other side of the lens. The image formed is inverted and of the same size as the object, as shown in the given figure.
It is given that the image of the needle is formed at a distance of 50 cm from the convex lens. Hence, the needle is placed in front of the lens at a distance of 50 cm. Object distance, u = −50 cm Image distance, v = 50 cm Focal length = f According to the lens formula, Hence, the power of the given lens is +4 D.જવાબ : Power of lens is defined as the reciprocal of its focal length. If P is the power of a lens of focal length F in metres, then
The S.I. unit of power of a lens is Dioptre. It is denoted by D. 1 dioptre is defined as the power of a lens of focal length 1 metre. ∴1 D = 1 m^{−1}જવાબ : Refractive index of a medium n_{m} is related to the speed of light in that medium v by the relation:
Where, c is the speed of light in vacuum/air The refractive index of diamond is 2.42. This suggests that the speed of light in diamond will reduce by a factor 2.42 compared to its speed in air.જવાબ : Refractive index of a medium n_{m} is given by,
જવાબ : Magnification produced by a spherical mirror is given by the relation,
Object distance, u = −10 cm v = 3 × (−10) = −30 cm Here, the negative sign indicates that an inverted image is formed at a distance ofજવાબ : Radius of curvature, R = 32 cm
Radius of curvature = 2 × Focal length (f) R = 2f Hence, the focal length of the given convex mirror is 16 cm.જવાબ : Radius of curvature, R = 20 cm
Radius of curvature of a spherical mirror = 2 × Focal length (f) R = 2f Hence, the focal length of the given spherical mirror is 10 cm.જવાબ : Magnification produced by a spherical mirror:
Object distance (u) = – 10 cm v = 3 × ( 10) = – 30 cm Therefore, the negative sign indicates that an inverted image is formed in front of the given concave mirror at a distance of 30 cm.જવાબ : Given: u = 10 cm, f = 15 cm and v = ?
Hence, the image is formed behind the mirror. It is erect, virtual and smaller than the object.
Material medium  Refractive index  Material medium  Refractive index 
Air  1.0003  Canada Balsam  1.53 
Ice  1.31  –  – 
Water  1.33  Rock salt  1.54 
Alcohol  1.36  –  – 
Kerosene  1.44  Carbon disulphide  1.63 
Fused quartz  1.46  Dense flint glass  1.65 
Turpentine oil  1.47  Ruby  1.71 
Benzene  1.50  Sapphire  1.77 
Crown glass  1.52  Diamond  2.42 
જવાબ : Lowest optical density = Air
Highest optical density = Diamond The optical density of a medium is directly related to its refractive index. A medium with the highest refractive index will have the highest optical density and viceversa. It can be observed from the table that air and diamond respectively have the lowest and highest refractive index. Hence, air has the lowest optical density and diamond has the highest optical density.જવાબ : Object distance (u) = – 20 cm
Object height (h) = 5 cm Radius of curvature (R) = 30 cm Radius of curvature = 2 × Focal length R = 2f f = 15 cm According to the mirror formula, The positive value of image height indicates that the image formed is erect. Hence, the image formed is erect, virtual, and smaller in size.જવાબ : Object distance (u) = – 27 cm
Object height (h) = 7 cm Focal length (f) = – 18 cm According to the mirror formula, The negative value of image height indicates that the image formed is inverted.જવાબ :
જવાબ :
જવાબ :
જવાબ : We can identify the three types of mirrors by looking at them. If the size of the image of an object is of the
same size as that of the object, then mirror is plane mirror. If the size of the image of an object increases as the object is brought closer to the mirror and the size of image is highly magnified when the object is very close to the mirror, then the mirror is concave mirror. If the size of the image is smaller and full length of the image of an object is seen, then the mirror is convex mirror.
જવાબ :
જવાબ : Refraction of light follows the following two laws :
જવાબ :
Convex lens  Concave lens 
1. It is thick in the middle and thin at edges.  1. It is thin in middle and thick at edges. 
2. When placed close to eye, it forms magnified image of an object. For example, if you place it close to your book, the words will appear large in size.  2. It forms diminished image of an object. If you place it close to your book, the words will appear small in size. 
જવાબ : Given: v = 50 cm, u = ?, P = ?
Since the image is equal to the size of the object, so the object is placed at a distance twice the focal length of the lens, i.e.
u = v = 2f= 50 cm
∴ u = 50 cm and f= 25 cm
Hence, the needle is placed at a distance of 50 cm in front of the lens.
Nowpower,
જવાબ : Yes, it will produce a complete image of the object. This can be verified experimentally as follows:
Procedure:
જવાબ : The ray diagram is shown below:

Focus 

Concave 

Real image


Diverging lens 

Convex 
જવાબ :
a. Diverging lens
b. Convex
c. Concave
d. Focus
e. Real image

Converging lens


Refraction 

One 
Hide  Show
જવાબ :
a. Refraction
b. One
c. Converging lens
Column I 
Column II 
(a) Mirror having magnification always equal to one (m = 1) 
(i) concave mirror 
(b) Mirror used to concentrate sunlight in reflecting solar cooker 
(ii) refraction 
(c) Image can be obtained on screen 
(iii) plane mirror 
(d) Bottom of a tank containing water appears to be raised due to 
(iv) convex lens 
(e) The lens having power – 2D 
(v) real image 
(f) The lens which is thicker at middle as compared to edges 
(vi) concave lens 
(g) Mirror used as rearview mirror in vehicles 
(vii) convex mirror 
જવાબ :
Column I 
Column II 
(a) Mirror having magnification always equal to one (m = 1) 
(iii) plane mirror 
(b) Mirror used to concentrate sunlight in reflecting solar cooker 
(i) concave mirror 
(c) Image can be obtained on screen 
(v) real image 
(d) Bottom of a tank containing water appears to be raised due to 
(ii) refraction 
(e) The lens having power – 2D 
(vi) concave lens 
(f) The lens which is thicker at middle as compared to edges 
(iv) convex lens 
(g) Mirror used as rearview mirror in vehicles 
(vii) convex mirror 
.
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