Reflection Of Light - Practice Test, Class 10 Science - Class 10 MCQ

• Light as a form of energy: Light is a form of energy that is visible to the human eye and travels in waves.


• Produced by a luminous object: Light is typically produced by objects that emit their own light, known as luminous objects.


• Luminous objects: These objects generate light through processes such as incandescence, fluorescence, or bioluminescence.


• Examples of luminous objects: The sun, light bulbs, and stars are all examples of luminous objects that produce light energy.


• Transparent vs. opaque objects: Transparent objects allow light to pass through them, while opaque objects block the passage of light.


• Non-luminous objects: Non-luminous objects do not emit their own light but can reflect light from other sources.

• Explanation:


• The moon is a non-luminous object as it does not emit light of its own.


• It reflects sunlight that hits its surface, making it visible to us at night.


• Unlike the sun, which is a luminous object that emits light due to nuclear fusion reactions happening in its core, the moon simply reflects light.


• Other examples of non-luminous objects include planets, asteroids, and comets.

• Definition: Reflection is the phenomenon in which incident light falling on a surface is sent back into the same medium.


• Process: When light rays hit a smooth surface, they bounce off in a predictable manner.


• Law of Reflection: The angle of incidence is equal to the angle of reflection. This means that the angle at which the light hits the surface is the same as the angle at which it bounces off.

• When light is incident on a polished surface, regular reflection takes place.


• Regular reflection occurs when light rays strike a smooth surface and reflect at the same angle as the incident angle.


• It results in a clear and well-defined image being formed.


• Regular reflection is also known as specular reflection.

• When an object undergoes regular reflection, the light rays hitting the object are reflected uniformly in a single direction.


• This type of reflection occurs on smooth and polished surfaces, such as mirrors.


• Regular reflection results in a clear and sharp image of the object being reflected.


• When light rays reflect off an object through regular reflection, the object appears visible to the observer.

• Plane Mirror: A plane mirror is a flat reflective surface that reflects light without distortion.


• Virtual Image: The image formed by a plane mirror is always virtual, which means it cannot be projected onto a screen. It appears to be behind the mirror at the same distance as the object is in front of the mirror.


• Erect Image: The image formed by a plane mirror is also erect, which means it is upright and not inverted.


• Same Size as Object: The virtual image formed by a plane mirror is the same size as the object.


• Distance: The image appears to be located at the same distance behind the mirror as the object is in front of the mirror.

• Definition: The centre of the sphere of which the spherical mirror forms a part is called the centre of curvature.


• Position: It lies on the principal axis of the mirror and is located behind the mirror.


• Distance: The distance between the pole of the mirror and the centre of curvature is called the radius of curvature.


• Characteristics: The centre of curvature is equidistant from all points on the mirror surface.

Focus is a point where light rays appears to meet. It is called real focus when there is actual intersection of light as in case of concave mirrors.

While in the case of convex mirror light rays are drawn back to meet at a point.

Therefore Concave mirrors have a real focus as it is formed by real intersection of light rays.

• Definition: A concave mirror is a converging mirror, meaning that it converges light rays that strike it parallel to its principal axis.


• Focal Point: Concave mirrors have a focal point where all the light rays parallel to the principal axis converge after reflection.


• Real Image: When an object is placed beyond the focal point of a concave mirror, a real inverted image is formed between the focal point and the mirror.


• Magnification: Concave mirrors can produce magnified images depending on the position of the object relative to the mirror.


• Applications: Concave mirrors are used in various optical devices such as telescopes, headlights, and makeup mirrors.

• Convex Mirrors: Convex mirrors are curved mirrors where the reflective surface bulges outwards. They have a virtual focus point behind the mirror.


• Image Characteristics: The image formed by a convex mirror is always virtual, upright (erect), and diminished in size.


• Virtual Image: A virtual image is formed when the light rays diverge after reflection. It cannot be projected onto a screen as it appears to be located behind the mirror.


• Upright Image: The image formed by a convex mirror is always upright, meaning it is in the same orientation as the object.


• Diminished Image: The image formed by a convex mirror is smaller in size compared to the actual object.


• Real and Magnified Image: Convex mirrors do not produce real images (images that can be projected onto a screen) or magnified images (where the size of the image is larger than the object).

• Virtual Image: A virtual image is formed when the reflected rays appear to diverge from a point behind the mirror. In this case, the image formed is virtual.



• Erect Image: An erect image is one that is upright and not inverted. Since the image formed is erect, it means that the top of the object is at the top of the image and vice versa.



• Magnified Image: A magnified image is larger than the object. In this case, the image formed is magnified.



• Position of the Object: The object must be placed between the pole of the mirror and the focus for a concave mirror to form a virtual, erect, and magnified image.

• Function: Dentists use concave mirrors to focus light on the tooth of a patient during examinations and procedures.


• Light Reflection: The concave mirror reflects light in a way that concentrates it to a specific point, allowing dentists to clearly see the tooth.


• Magnification: The concave mirror can also magnify the image of the tooth, helping dentists to identify any issues or problems more easily.


• Adjustability: Dentists can adjust the position of the concave mirror to get the best possible view of the tooth they are working on.


• Precision: The use of a concave mirror in dentistry allows for more precise and accurate dental procedures.

• Given: Object distance, u = 2m


• Shift in object position: s = 0.5m


• Distance between object and image: d = ?


• Formula: 1/f = 1/u + 1/v


• Calculations:
  
  
  
  • Using the mirror formula, 1/f = 1/u + 1/v
  
  
  • Given u = 2m, s = 0.5m
  
  
  • Calculating the new object distance, u' = u + s = 2 + 0.5 = 2.5m
  
  
  • Substitute u' in the formula: 1/f = 1/2.5 + 1/v
  
  
  • 1/f = 0.4 + 1/v
  
  
  • 1/v = 1/f - 0.4
  
  
  • Given f = 2u = 4m (Since the mirror is a plane mirror, the focal length is double the object distance)
  
  
  • Substitute f = 4m in the equation: 1/v = 1/4 - 0.4 = 0.25 - 0.4 = -0.15
  
  
  • Therefore, v = -1/0.15 = -6.67m (Negative sign indicates the image is behind the mirror)
  
  
  
  


• Distance between object and its image: d = |u - v| = |2 - (-6.67)| = |2 + 6.67| = 8.67m ≈ 8.7m ≈ 5m

• Definition: When a ray of light is incident normally on a plane mirror, it means the incident ray is perpendicular to the mirror surface.


• Angle of Incidence: The angle between the incident ray and the normal to the mirror surface is 0 degrees.


• Angle of Reflection: According to the law of reflection, the angle of reflection is equal to the angle of incidence.


• Calculation: Since the incident ray is perpendicular to the mirror, the angle between the incident and reflected rays is 0 degrees.


• Answer: The angle between the incident and reflected rays when a ray of light is incident normally on a plane mirror is 0 degrees (Option D).

• Real Image: A real image is an image that is formed by the actual convergence of light rays. It can be captured on a screen or surface, making it visible to the human eye.

• Given: Angle of reflection = 50 degrees


• Angle of incidence = Angle of reflection (according to the law of reflection)


• Let the angle between incident ray and reflected ray be x degrees


• According to the properties of a straight line, the sum of angles on the same side of the transversal is 180 degrees


• Therefore, angle of incidence + angle of reflection + angle between incident ray and reflected ray = 180 degrees


• Substitute the given values:




• 50 degrees + 50 degrees + x degrees = 180 degrees


• 100 degrees + x degrees = 180 degrees


• x degrees = 180 degrees - 100 degrees


• x = 80 degrees

• Two plane mirrors: Plane mirrors are essential for making a periscope as they reflect light without distorting the image.


• Cardboard or a similar material: This will be used to create the structure of the periscope.


• Scissors: To cut the cardboard to the desired shape and size.


• Glue or tape: To attach the mirrors to the cardboard and hold the periscope together.


• Ruler and pencil: To measure and mark the cardboard before cutting.

1. Cut the cardboard: Cut two rectangular pieces of cardboard of the same size for the sides of the periscope.


2. Attach the mirrors: Glue or tape one mirror at a 45-degree angle on each cardboard piece.


3. Assemble the periscope: Place the two cardboard pieces together to form a right angle, with the mirrors facing each other.


4. Decorate (optional): You can decorate the periscope with paint or other materials to make it more visually appealing.


5. Use the periscope: Look through one end of the periscope while pointing the other end towards the object you want to see. The mirrors will reflect the image, allowing you to see around corners or over obstacles.

• A convex mirror has a wider field of view compared to other types of mirrors.


• Convex mirrors have a reflective surface that bulges outwards, causing light rays to diverge.


• Due to this outward bulge, convex mirrors can reflect a larger area of the surroundings.


• Convex mirrors are commonly used in vehicles as side mirrors to provide a wider field of view for the driver.

• Concave mirrors have a reflective surface that curves inwards, causing light rays to converge.


• Concave mirrors are used for focusing light in applications such as telescopes and makeup mirrors.


• They do not provide as wide of a field of view as convex mirrors due to the converging nature of the reflected light.

• Plane mirrors have a flat reflective surface that reflects light without distortion.


• They provide an accurate reflection of objects but do not widen the field of view.


• Plane mirrors are commonly used in bathrooms and dressing rooms for personal grooming purposes.

• Cylindrical mirrors have a curved reflective surface that is cylindrical in shape.


• They are used in applications where a specific type of reflection is required, such as in certain optical instruments.


• Cylindrical mirrors do not typically provide a wider field of view compared to convex mirrors.

Therefore, the convex mirror has a wider field of view compared to concave, plane, and cylindrical mirrors due to its outward bulging shape that allows for a broader reflection of the surroundings.

• Given: Focal length = 15 cm


• Formula: The relationship between the focal length (f) and the radius of curvature (R) for a concave mirror is given by the formula: 1/f = 1/R


• Substitute the given value: Substitute the given focal length value into the formula: 1/15 = 1/R


• Solve for R: Rearrange the formula to solve for R: R = 15 cm


• Answer: The radius of curvature of the concave mirror is 30 cm (Option B)

• Focal Length: The focal length of a mirror is the distance between the mirror's focal point and its center. In this case, the focal length is 15 cm.


• Convex Mirror: A convex mirror is a type of mirror where the reflective surface bulges outwards. It diverges light rays and forms virtual, upright, and diminished images. Convex mirrors have a positive focal length.


• Identifying the Type of Mirror: Since the given focal length is 15 cm, which is a positive value, it indicates that the mirror is a convex mirror. Therefore, the answer is option C: Convex mirror.

• Ray of Light: When a ray of light passes through the center of curvature, it retraces its path.


• Retracing Path: This phenomenon occurs because the angle of incidence is equal to the angle of reflection when the light ray passes through the center of curvature.


• Center of Curvature: The center of curvature is located on the principal axis of a concave mirror or a convex lens.


• Focusing Point: The focus is another point on the principal axis where light rays parallel to the axis converge or appear to diverge from after reflection or refraction.


• Vertex and Pole: The vertex is the point where the principal axis intersects the mirror or lens, while the pole is the center of the mirror or lens.

• Concave Mirror: A concave mirror is a curved mirror where the reflective surface bulges inwards.


• Focus: The focus of a concave mirror is the point where parallel rays of light converge or appear to diverge from after reflection.


• Image Formation: When an object is placed at the focus of a concave mirror, the reflected rays will be parallel to each other after reflection.


• Image Location: The parallel rays of light will never meet or converge, and they will appear to meet at a point at infinity.


• Image Characteristics: The image formed at infinity will be highly diminished, virtual, and cannot be projected on a screen.

• Transparency: Transparency refers to the property of allowing light to pass through. Butter paper is an example of a translucent object as it allows some light to pass through but scatters it in the process. This is why we can see shapes and colors through butter paper, but not as clearly as we would through a transparent object.


• Example: When you hold butter paper up to a light source, you can see the light shining through it, but the image is not as clear as it would be with a transparent object like clear glass.


• Function: Butter paper is commonly used in baking to prevent food from sticking to pans and trays. Its translucent nature allows bakers to see the food without removing it from the pan, making it easier to monitor the cooking process.


• Comparison: In contrast, opaque objects do not allow any light to pass through, while luminous objects emit their own light. Butter paper falls in between these two categories, making it a perfect example of a translucent object.

• Given: Object size = 2.0 cm, object distance = radius of curvature


• Formula: Magnification (M) = -v/u


• Using mirror formula: 1/f = 1/v + 1/u


• Since the object is at the radius of curvature: u = -R


• Calculating the focal length: f = R/2


• Substitute the values: 1/f = 1/v - 1/R


• Solving for v: v = 2R


• Calculating magnification: M = -v/u = -2R / -R = 2


• Using magnification formula: M = -i/o


• Substitute the values: 2 = -i/2.0


• Solving for image size (i): i = -4.0 cm

An incident ray which passes through the center of curvature C of the mirror is reflected back along its own path (since it is normally incident on the mirror).