Reflection And Refraction - MCQ Test (22-11-2017) - Class 10 MCQ

The magnification of plane mirror is 1 since the size of the image is the same as the size of the object. The distance of the image from the mirror is the same as the distance of the object from the mirror.

Magnification (m) 

For a fixed incident ray, the angle of the reflection will be twice the angle through which the mirror has rotated. After reflection, a ray of light is reflected by an angle about the normal. The reflected ray follows the law of reflection according to which the angle of reflection is always equal to the angle of incidence. When the mirror is rotated by an angle Q, the normal (which is perpendicular to the mirror) also rotates by the same angle Q. So the ray of light is also rotated at an angle Q about the normal. Hence, the total rotation of the reflected ray is given by:

Q (angle between the incident ray and normal at the point of incidence) + Q (angle between and the new reflected ray and the new normal at the point of incidence) = 2Q

If the upper half of the concave mirror is covered, the amount of light that gets reflected from the mirror will be reduced. Consequently, the brightness of the image that is formed on the screen will be reduced.

The experiment may be performed on the same wall as the window to obtain a sharp image since a concave mirror mostly forms images on the same side as that of the object. The object and the image are on the same side of the concave mirror, except when the object is placed between the pole and the focus.

A convex mirror always forms an erect, and a virtual and diminished image, for any position of the object.

Plane mirrors are generally used to demonstrate reflection of light in laboratories since it is easier to draw the normal to a plane mirror at the point of incidence and trace the reflected ray.

A lens has two spherical surfaces. An imaginary straight line passing through the two centres of curvature of a lens is called its principal axis. The principal axis of the lens should be parallel to the length of the optical bench while performing an experiment, so that errors in experimental values are avoided.

Both the statements are correct. A real image is always inverted. A virtual image is always erect.

The frequency of light depends on the source of light and remains the same during refraction. The speed of the light changes when a ray of light passes from one medium to another. The speed of light is higher in a rarer medium than a denser medium. A ray of light travelling from a rarer medium to a denser medium slows down, due to which there is a change in the wave-length.

The mirror can be either a plane mirror or a convex mirror. A convex mirror always forms an erect, and a virtual and diminished image, for any position of the object. A plane mirror also forms an erect image.

The value of magnification, m = 1, signifies that the image is of the same size as that of the object.

Magnification (m)  = 1

When light enters from one medium into another, the frequency of light does not change. Speed, wavelength and amplitude may change depending upon the optical density of the two mediums.

If the object is placed at the focus of the concave mirror, the image will be formed at infinity. The image will be highly enlarged, and will be real and inverted.

Linear magnification (m) has no unit since it is the ratio of  the height of the image to the height of the object. Magnification produced by a spherical mirror gives the relative extent to which the image of an object is magnified with respect to the object.
m

An image formed by a plane mirror is always erect, virtual and of the same size as that of the object. A convex mirror always forms an erect, virtual and a diminished image, for any position of the object.

All the given statements are correct. The speed of all colours is same in air or vacuum i.e. 3×10⁸ms⁻¹. But the speed of all colours is different in a denser medium. Refractive index has no unit since it is a ratio. The absolute refractive index of a medium (n_m) is given by n_m = c/v where c is the speed of light in air, and v is the speed of light in the medium.

The power of a lens is the reciprocal of its focal length. It is a measure of the degree of convergence or divergence of light rays achieved by a particular lens. The power of a convex lens is positive.

Given, focal length = 40 cm or 0.40 m
Therefore, Power of the given convex lens 

Concave mirrors are used by dentist to see the large images of teeth of patients since concave mirrors form enlarged images. Concave mirrors are also used for shaving purpose. Convex mirrors form diminished images. They are used as rear view mirrors in cars, motorcycles, scooters, etc since they giave a wide field of view.

The spherical mirror and the spherical lens - both are concave. The distance of the principal focus measured from the pole is called the focal length. According to the New Cartesian Sign Convention, the focal length of a concave mirror as well as that of a concave lens is considered negative.

According to New Cartesian Sign Convention for a convex lens, distance of the object from the pole is negative and the focal length of a convex lens is  taken as positive.

A convex lens (converging lens) is thicker at the middle than at the edges. A concave lens (diverging lens) is thicker at the edges than at the middle.

When a lemon is kept in water in a bowl, and is viewed from the outside, it appears larger than its actual size due to refraction. When reflected rays of light travel from the lemon (which is in water) towards the eye (which is in air), the rays travel from a denser medium to a rarer medium and they bend away from the normal to the water surface.

A real image is an image which is located in the plane of convergence for the light rays that originate from a given object. If a screen is placed in the plane of a real image the image will generally become visible on the screen. Examples of real images include the image seen on a cinema screen (the source being the projector), the image produced on a detector in the rear of a camera, and the image produced on an eyeball retina

An image formed by a convex lens is always real and inverted except when the object is between the optical centre and the focus F₁

A concave mirror is used in ophthalmoscope to examine throat and ear. A concave mirror forms an enlarged image of the part being examined by a physician. An image formed by a plane mirror is of an equal size as that of the object, whereas a convex mirror always forms a diminished image, for any position of the object.

Clay cannot be used to make a lens. Only transparent materials can be used to make a lens.

The net power of the resultant lens is given by the algebraic powers of the individual powers.
Equivalent power of the lens combination, P = P₁ + P₂ = (+4 D) + (-3 D) = +1 D

A ray of light passing from an optically denser medium to an optically rarer medium, bends away from the normal, and a ray of light passing from an optically rarer medium to an optically denser medium, bends toward the normal.

Upon passage through a triangular glass prism, the white light is separated into its component colors - red, orange, yellow, green, blue, indigo and violet. The separation of visible light into its different colors is known as dispersion. The light that will emerge out of the combination of the two prisms, will be white in colour.

Out of water, kerosene, turpentine, and diamond, light travels the fastest in water. The speed of light is higher in a optically rarer medium than in a optically denser medium.