Light — Reflection and Refraction — Important Questions
47 questions
With answersCBSE format
SUMMARY: This chapter focuses on the phenomena of reflection and refraction of light, explaining their principles and applications. KEY TOPICS: reflection of light, laws of reflection, plane mirrors, spherical mirrors, refraction of light, laws of refraction, refractive index, lenses, lens formula, magnification
What is the angle of incidence if the angle of reflection is 30 degrees?
A30 degrees
B60 degrees
C90 degrees
D45 degrees
Check answerHide answer
Correct answer: Option 1 — 30 degrees
Q21 Mark
Which of the following statements is true regarding the laws of reflection?
AThe angle of incidence is equal to the angle of refraction.
BThe incident ray, reflected ray, and normal all lie in the same plane.
CThe angle of incidence is always greater than the angle of reflection.
DReflection occurs only on smooth surfaces.
Check answerHide answer
Correct answer: Option 2 — The incident ray, reflected ray, and normal all lie in the same plane.
Q31 Mark
What type of mirror is used in a rear-view mirror of vehicles?
AConcave mirror
BConvex mirror
CPlane mirror
DSpherical mirror
Check answerHide answer
Correct answer: Option 2 — Convex mirror
Q41 Mark
What is the refractive index of a medium if the speed of light in vacuum is 3 x 10^8 m/s and in the medium it is 2 x 10^8 m/s?
A1.5
B0.67
C2.0
D1.0
Check answerHide answer
Correct answer: Option 1 — 1.5
Q51 Mark
Which lens type is used to correct hyperopia (farsightedness)?
AConcave lens
BConvex lens
CBifocal lens
DCylindrical lens
Check answerHide answer
Correct answer: Option 2 — Convex lens
Q61 Mark
What is the focal length of a concave mirror if the object distance is 30 cm and the image distance is -15 cm?
A10 cm
B15 cm
C20 cm
D25 cm
Check answerHide answer
Correct answer: Option 1 — 10 cm
Q71 Mark
Which of the following is NOT a characteristic of the image formed by a plane mirror?
AUpright
BVirtual
CSame size as the object
DInverted
Check answerHide answer
Correct answer: Option 4 — Inverted
Q81 Mark
What is the formula for calculating magnification in lenses?
AM = h_i / h_o
BM = v / u
CM = f / d
DM = u / v
Check answerHide answer
Correct answer: Option 1 — M = h_i / h_o
Q91 Mark
If a ray of light passes from air into water, what happens to its speed?
AIncreases
BDecreases
CRemains the same
DBecomes zero
Check answerHide answer
Correct answer: Option 2 — Decreases
Q101 Mark
What is the principal focus of a concave lens?
AReal and inverted
BVirtual and upright
CReal and upright
DVirtual and inverted
Check answerHide answer
Correct answer: Option 2 — Virtual and upright
Q111 Mark
Which of the following describes the term 'refraction'?
ABending of light when it reflects off a surface
BBending of light when it passes from one medium to another
CScattering of light in different directions
DAbsorption of light by a medium
Check answerHide answer
Correct answer: Option 2 — Bending of light when it passes from one medium to another
Q121 Mark
What is the relationship between the object distance (u), image distance (v), and focal length (f) in a convex lens?
A1/f = 1/v + 1/u
B1/f = 1/u - 1/v
Cf = u + v
Df = u - v
Check answerHide answer
Correct answer: Option 1 — 1/f = 1/v + 1/u
Q131 Mark
In which type of mirror does the image appear larger than the object?
APlane mirror
BConvex mirror
CConcave mirror
DSpherical mirror
Check answerHide answer
Correct answer: Option 3 — Concave mirror
Q141 Mark
What happens to the light ray when it strikes the boundary between two different media at an angle greater than the critical angle?
AIt is refracted
BIt is reflected
CIt is absorbed
DIt is scattered
Check answerHide answer
Correct answer: Option 2 — It is reflected
Q151 Mark
Which of the following is a property of the image formed by a convex lens?
AAlways real
BAlways virtual
CCan be real or virtual depending on the position of the object
DAlways inverted
Check answerHide answer
Correct answer: Option 3 — Can be real or virtual depending on the position of the object
Short Answer Questions10 questions
Q163 Marks
What are the laws of reflection?
View sample solutionHide solution
The laws of reflection state that (1) the incident ray, the reflected ray, and the normal at the point of incidence all lie in the same plane, and (2) the angle of incidence is equal to the angle of reflection.
Q173 Marks
Define the term 'refractive index'.
View sample solutionHide solution
The refractive index of a medium is defined as the ratio of the speed of light in vacuum to the speed of light in that medium. It indicates how much light bends when entering the medium.
Q183 Marks
What is the difference between a concave mirror and a convex mirror?
View sample solutionHide solution
A concave mirror curves inward and can converge light rays to a focal point, while a convex mirror curves outward and diverges light rays, making it useful for wider field of view.
Q193 Marks
State the lens formula and explain its components.
View sample solutionHide solution
The lens formula is given by 1/f = 1/v - 1/u, where f is the focal length, v is the image distance from the lens, and u is the object distance from the lens. This formula helps in determining the position and nature of the image formed by a lens.
Q203 Marks
What is the significance of the focal point in a concave lens?
View sample solutionHide solution
In a concave lens, the focal point is virtual and located on the same side as the object. Light rays diverge after passing through the lens, and the focal point is where the rays appear to originate from when extended backward.
Q213 Marks
Explain the phenomenon of total internal reflection.
View sample solutionHide solution
Total internal reflection occurs when a light ray traveling in a denser medium hits the boundary with a less dense medium at an angle greater than the critical angle, causing all the light to be reflected back into the denser medium instead of refracting.
Q223 Marks
How does the angle of incidence affect the angle of reflection?
View sample solutionHide solution
According to the laws of reflection, the angle of incidence is always equal to the angle of reflection. This means that as the angle of incidence increases, the angle of reflection increases correspondingly.
Q233 Marks
Describe how a plane mirror forms an image.
View sample solutionHide solution
A plane mirror forms an image by reflecting light rays that strike its surface. The image formed is virtual, upright, and of the same size as the object, located at the same distance behind the mirror as the object is in front of it.
Q243 Marks
What is magnification in the context of lenses?
View sample solutionHide solution
Magnification is the ratio of the height of the image to the height of the object. It indicates how much larger or smaller the image appears compared to the actual object and can be calculated using the formula magnification (m) = height of image (h') / height of object (h).
Q253 Marks
Explain how light behaves when it passes from air into water.
View sample solutionHide solution
When light passes from air into water, it slows down and bends towards the normal due to the higher refractive index of water compared to air. This bending of light is an example of refraction.
Long Answer Questions6 questions
Q266 Marks
Explain the laws of reflection and how they apply to plane mirrors. Provide a diagram to illustrate your answer.
View sample solutionHide solution
The laws of reflection state that: 1) The angle of incidence is equal to the angle of reflection, and 2) The incident ray, the reflected ray, and the normal to the surface at the point of incidence all lie in the same plane. In the case of plane mirrors, when light rays strike the mirror, they reflect off in such a way that the angle at which they hit the mirror (angle of incidence) is equal to the angle at which they leave (angle of reflection). This property is used in everyday applications such as in personal grooming mirrors, where a clear image is produced due to the uniform reflection of light.
Q276 Marks
Describe the characteristics of images formed by concave mirrors. Include the types of images based on the position of the object.
View sample solutionHide solution
Concave mirrors can produce both real and virtual images depending on the position of the object relative to the focal point and the center of curvature. When the object is beyond the center of curvature, a real, inverted, and diminished image is formed. If the object is at the center of curvature, the image is real, inverted, and of the same size. When the object is between the center of curvature and the focal point, a real, inverted, and enlarged image is produced. However, if the object is placed between the focal point and the mirror, a virtual, upright, and enlarged image is formed. These characteristics are crucial in applications such as shaving mirrors and reflectors.
Q286 Marks
What is refraction of light? Explain the laws of refraction and how they differ from the laws of reflection.
View sample solutionHide solution
Refraction of light is the bending of light rays as they pass from one medium to another due to a change in speed. The laws of refraction, also known as Snell's laws, state that: 1) The incident ray, the refracted ray, and the normal at the point of incidence all lie in the same plane, and 2) The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant, known as the refractive index (n). This differs from the laws of reflection, where the angles of incidence and reflection are equal, and there is no change in the medium. Refraction is essential in understanding how lenses work and in applications such as eyeglasses and cameras.
Q296 Marks
Define refractive index and explain how it is calculated using the speed of light in different media.
View sample solutionHide solution
The refractive index (n) of a medium is defined as the ratio of the speed of light in a vacuum (c) to the speed of light in that medium (v). It is calculated using the formula n = c/v. A higher refractive index indicates that light travels slower in that medium compared to a medium with a lower refractive index. For example, the refractive index of glass is typically around 1.5, meaning light travels 1.5 times faster in a vacuum than in glass. This concept is crucial in understanding how light bends when entering different materials, which is fundamental in the design of optical devices.
Q306 Marks
Explain the concept of lenses and differentiate between convex and concave lenses with examples.
View sample solutionHide solution
Lenses are transparent optical devices that refract light to converge or diverge rays. Convex lenses, also known as converging lenses, are thicker at the center than at the edges and can focus parallel rays of light to a point known as the focal point. They are used in applications such as magnifying glasses and cameras. Concave lenses, or diverging lenses, are thinner at the center and thicker at the edges, causing parallel rays of light to diverge as if they are coming from a focal point behind the lens. They are commonly used in eyeglasses for nearsightedness. The distinct properties of these lenses are essential in various optical instruments.
Q316 Marks
Derive the lens formula for a thin lens and explain its significance in optics.
View sample solutionHide solution
The lens formula for a thin lens is given by 1/f = 1/v - 1/u, where f is the focal length, v is the image distance, and u is the object distance. This formula is derived from the geometry of light rays passing through the lens and the principles of refraction. The significance of the lens formula lies in its ability to predict the position and nature of the image formed by a lens based on the object's position. It is fundamental in optical applications such as photography, where understanding image formation is crucial for capturing clear images.
Assertion–Reason Questions8 questions
Q321 Mark
Assertion (A): The angle of incidence is always equal to the angle of reflection when light reflects off a surface.
Reason (R): This is known as the first law of reflection.
Show explanationHide explanation
Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q331 Mark
Assertion (A): A concave mirror can produce both real and virtual images.
Reason (R): Concave mirrors can focus light to form images at various distances depending on the object's position.
Show explanationHide explanation
Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q341 Mark
Assertion (A): The refractive index of a medium is defined as the ratio of the speed of light in vacuum to the speed of light in that medium.
Reason (R): This definition helps in understanding how light bends when it enters different media.
Show explanationHide explanation
Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q351 Mark
Assertion (A): A plane mirror produces a real image of an object placed in front of it.
Reason (R): The image formed by a plane mirror is always virtual and upright.
Show explanationHide explanation
Correct answer: Option 4 —
A is false, but R is true.
Q361 Mark
Assertion (A): The magnification produced by a lens is the ratio of the height of the image to the height of the object.
Reason (R): This ratio helps in determining how much larger or smaller the image is compared to the object.
Show explanationHide explanation
Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q371 Mark
Assertion (A): Light rays converge at the focal point of a convex lens.
Reason (R): This property is due to the lens's ability to refract light rays towards a common point.
Show explanationHide explanation
Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q381 Mark
Assertion (A): The second law of reflection states that the incident ray, the reflected ray, and the normal to the surface all lie in the same plane.
Reason (R): This is a fundamental principle of how light behaves during reflection.
Show explanationHide explanation
Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q391 Mark
Assertion (A): When light passes from a denser medium to a rarer medium, it bends towards the normal.
Reason (R): This statement is incorrect; light actually bends away from the normal in this scenario.
Show explanationHide explanation
Correct answer: Option 4 —
A is false, but R is true.
Statement-Based Questions8 questions
Q401 Mark
Statement 1: The angle of incidence is always equal to the angle of reflection.
Statement 2: Reflection of light occurs when it passes from one medium to another.
Show answerHide answer
Correct answer: Option 1 —
Both statements are true.
Q411 Mark
Statement 1: A concave mirror can produce a virtual image.
Statement 2: The focal length of a convex mirror is positive.
Show answerHide answer
Correct answer: Option 1 —
Both statements are true.
Q421 Mark
Statement 1: The refractive index of a medium is defined as the ratio of the speed of light in vacuum to the speed of light in that medium.
Statement 2: Light always bends towards the normal when it enters a denser medium.
Show answerHide answer
Correct answer: Option 1 —
Both statements are true.
Q431 Mark
Statement 1: The laws of reflection apply only to plane mirrors.
Statement 2: Spherical mirrors can be either concave or convex.
Show answerHide answer
Correct answer: Option 2 —
Only Statement 1 is true.
Q441 Mark
Statement 1: The lens formula is given by 1/f = 1/v - 1/u.
Statement 2: Magnification is defined as the ratio of the height of the image to the height of the object.
Show answerHide answer
Correct answer: Option 1 —
Both statements are true.
Q451 Mark
Statement 1: A ray of light passing through the center of curvature of a concave mirror will reflect back along the same path.
Statement 2: The image formed by a convex lens is always real and inverted.
Show answerHide answer
Correct answer: Option 3 —
Only Statement 2 is true.
Q461 Mark
Statement 1: Refraction occurs due to the change in speed of light when it travels from one medium to another.
Statement 2: The angle of refraction is always greater than the angle of incidence when light enters a denser medium.
Show answerHide answer
Correct answer: Option 4 —
Both statements are false.
Q471 Mark
Statement 1: In a plane mirror, the image formed is always virtual and upright.
Statement 2: The focal point of a concave lens is on the same side as the object.
Show answerHide answer
Correct answer: Option 1 —
Both statements are true.
