Quick Revision of Light and Reflection in Differet Types of Mirrors - Interactive
Vidya Mine
www.vidyamine.com
Chapter 13: Light
Class: 08 |
Subject: Science
Topic: Quick Revision of Light and Reflection in Differet Types of Mirrors
Assertion Reasoning Questions
1. Assertion (A): The rainbow has only primary colours.
Reason (R): Rainbow is formed due to lateral inversion.
a)Both A and R are true, and R is the correct explanation of A
b)Both A and R are true, but R is not the correct explanation of A
c)A is true, but R is false
d)A is false, but R is true
Hint: Check reason for rainbow formation.
Solution: Rainbow has spectrum colours and forms due to dispersion, not lateral inversion.
Was this solution helpful?
Was it too long or confusing?
Fill In The Blanks
1. The angle of incidence is always equal to the angle of ________ in reflection.
Hint: Refer to laws of reflection.
Solution: First law of reflection states i = r.
Was this solution helpful?
Was it too long or confusing?
2. Multiple images can be formed using two plane mirrors kept at an angle. The number of images is given by the formula _______.
Hint: Mention angle-based formula.
Solution: Formula: 360/xΒ° - 1, where x is angle between mirrors.
Was this solution helpful?
Was it too long or confusing?
Case Study Based Questions
1. During a craft activity, students made kaleidoscopes using two mirrors placed at a 60Β° angle. When they looked through, they saw multiple reflections. Their teacher explained the formula to find the number of images: (360/ΞΈ) - 1. Using the angle of 60Β°, they calculated the result. (a) How many images are formed when two mirrors are placed at a 60Β° angle?
(b) Which formula is used to calculate the number of images and what does each symbol represent?
Hint: Apply multiple reflection formula.
Solution: (a) When two mirrors are placed at a 60Β° angle, the number of images formed is given by the formula: (360/ΞΈ) - 1. Substituting 60Β° gives (360/60) - 1 = 6 - 1 = 5 images.
(b) The formula used is (360/ΞΈ) - 1, where ΞΈ is the angle between the mirrors. This equation calculates the total number of reflections seen between angled mirrors. The smaller the angle, the more images are formed. This principle is often used in kaleidoscopes, where colorful and symmetrical image patterns are created based on the arrangement and angle of mirrors inside the tube.
Was this solution helpful?
Was it too long or confusing?
2. In a science class experiment, students directed a light ray at a plane mirror at an angle of 30Β° to the normal. They observed that the ray reflected at the same angle on the other side. The teacher explained that this followed the law of reflection, where angle of incidence equals angle of reflection. (a) What is the angle of reflection if the angle of incidence is 30Β°?
(b) Which law is demonstrated in this experiment and how is it stated?
Hint: Link incidence and reflection angles.
Solution: (a) If the angle of incidence is 30Β°, then by the law of reflection, the angle of reflection will also be 30Β°. This is because the law states that both angles are always equal.
(b) The law demonstrated is the Law of Reflection, which states: "The angle of incidence is equal to the angle of reflection." It also states that the incident ray, the reflected ray, and the normal all lie in the same plane. This law is fundamental in optics and is used in the design of mirrors, periscopes, and other light-based instruments.
Was this solution helpful?
Was it too long or confusing?
Descriptive Questions
1. What is lateral inversion? Give an example.
Hint: Mention example and definition.
Solution: Plane mirrors laterally invert the reflected image.A plane mirror reflects light in such a way that the left and right sides of an object appear reversed, a phenomenon called lateral inversion. This occurs because the mirror reflects the light rays back at the same angle at which they strike it, but the orientation across the horizontal axis flips. As a result, text seen in a mirror appears backward, and actions like raising your right hand seem to be done with the left in the reflection. Despite this inversion, the size and distance of the image remain the same, making plane mirrors useful for daily activities and optical devices.
Was this solution helpful?
Was it too long or confusing?
2. Differentiate between regular and diffused reflection with examples.
Hint: Mention surface type and light behavior.
Solution: Smooth surfaces give regular; rough cause irregular reflection.When light strikes a smooth surface, such as a polished mirror or calm water, it reflects at consistent angles, resulting in regular reflection. This allows clear and well-defined images to form. In contrast, when light hits a rough or uneven surface like paper or a wall, the rays scatter in multiple directions because each point of the surface reflects light at different angles. This phenomenon is called irregular or diffused reflection. Although no clear image forms in irregular reflection, it is crucial for visibility, allowing us to see non-shiny objects around us by scattering light uniformly into our eyes.
Was this solution helpful?
Was it too long or confusing?
3. Why can a blind spot not be corrected by lens or glasses?
Hint: Relate to retina and optic nerve junction.
Solution: Blind spot has no rods/cones; hence unresponsive to light.The blind spot, or optic disc, is a region on the retina where the optic nerve exits the eye, and no photoreceptor cellsβrods or conesβare present. As a result, this area is completely insensitive to light and cannot detect visual information. In everyday life, the brain compensates for this lack of visual input by filling in the missing details based on surrounding information, so we are generally unaware of the blind spot. Special tests, however, can reveal its presence. Understanding the blind spot is crucial in fields like ophthalmology and helps explain certain visual phenomena.
Was this solution helpful?
Was it too long or confusing?
4. List the characteristics of an image formed by a plane mirror.
Hint: List features of plane mirror image.
Solution: Plane mirror images are upright, virtual, same size and laterally inverted.When an object is placed in front of a plane mirror, the image formed has specific characteristics: it is upright, virtual, of the same size as the object, and laterally inverted (left and right are swapped). Unlike real images that can be projected onto a screen, virtual images cannot be caught physically because the light rays only appear to come from behind the mirror. This property makes plane mirrors useful for daily activities such as grooming and decoration. The distance of the image behind the mirror is exactly equal to the object's distance in front of it.
Was this solution helpful?
Was it too long or confusing?
5. Why does sunlight appear white although it's a mixture of seven colours?
Hint: Link perception and light composition.
Solution: (b) The formula used is (360/θ) - 1, where θ is the angle between the mirrors. This equation calculates the total number of reflections seen between angled mirrors. The smaller the angle, the more images are formed. This principle is often used in kaleidoscopes, where colorful and symmetrical image patterns are created based on the arrangement and angle of mirrors inside the tube.
