Questions of Assertion Reason Chapter 9 Light – Reflection and Refraction Science CBSE Class 10 are very simple to understand as this chapter deals with Light and Laws of reflections. To solve assertion reason type questions of science, deeper understanding of concept about Light – Reflection and Refraction is required. In order to help the student in solving Assertion Reason type of questions, detailed process is explained.
How to solve Assertion Reason Type Questions?
In Assertion-Reason type of question, two statements are given, first is Assertion and second is called Reason. Student must have to think critically about both the statements in Assertion Reason Questions, since it combines multiple choice questions and true/false type of questions which requires a higher level of understanding.
How many types are there of Assertion Reason Type Questions?
Assertion-Reason type of questions can be asked either with four MCQ options or with five MCQ options. First four options are same in both the cases only one more options is being provided i.e. last one. One extra option increases the difficulty level of the questions.
In assertion reason type of questions, all 4 or 5 options are same for each question, which are as:
(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
(c) Assertion (A) is true but reason (R) is false.
(d) Assertion (A) is false but reason (R) is true.
(e) Both Assertion and Reason are false.
Then a question haunts in every student’s mind, which option is correct and when?
This can be understood clearly with the following table:
| Assertion (A) | Reason (R) | MCQ Options (Fixed for all questions) |
|---|---|---|
| If True | True | (a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A). |
| If True | True | (b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A). |
| If True | False | (c) Assertion (A) is true but reason (R) is false. |
| If False | True | (d) Assertion (A) is false but reason (R) is true. |
| If False | False | (e) Both Assertion and Reason are false. |
Now, lets practice some Assertion Reason Questions of Science Chapter 9 Light – Reflection and Refraction.
Read instructions carefully before answering the questions.
For question given below, two statements are given- one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both A and R are true and R is correct explanation of the assertion.
(b) Both A and R are true but R is not the correct explanation of the assertion.
(c) A is true but R is false.
(d) A is false but R is true.
Question.1.
Assertion: If a ray of light is incident on a convex mirror along its principal axis, then the angle of incidence as well as the angle of reflection for a ray of light will be zero.
Reason: A ray of light going towards the centre of curvature of a convex mirror is reflected back along the same path.
Ans.1. (b)
Question.2.
Assertion: Linear magnification of a mirror has no unit.
Reason: The ratio of height of the image to the height of the object is the linear magnification produced by mirror.
Ans.2. (a)
Linear magnification of a mirror is the ratio of height of the image (cm) and the height of the object (cm) and it has no unit.
Question.3.
Assertion: Light is able to reach earth from the sun.
Reason: Light rays can travel in vacuum.
Ans.3. (a)
Question.4.
Assertion: Property of converging of a convergent lens does not remain same in all media.
Reason: Property of lens whether the ray is diverging or converging is independent of the surrounding medium.
Ans.4. (c)
A convex lens made of glass behaves as a convergent lens when placed in air or water. However when the same lens is immersed in carbon disulphide (n = 1.63), it behaves as a divergent lens. Therefore when a convergent lens is placed inside a transparent medium of refractive index greater than that of material of the lens, it behaves as a divergent lens. Behaviour of a lens depends on the refractive index of a surrounding medium.
Question.5.
Assertion: We can decide the nature of a mirror by observing the size of erect image in the mirror.
Reason: The minimum distance between a real object and its real image in a concave mirror is non zero.
Ans.5. (d)
Question.6.
Assertion: A convex lens is made of two different materials. A point object is placed on the principal axis. The number of images formed by the lens will be two.
Reason: The image formed by convex lens is always virtual.
Ans.6. (c)
Since the lens is made of two different materials of different refractive indices, there will be two different focal lengths of the lens. Hence two images will be formed. The image formed by convex lens is always real except in case when object is placed between optical centre and focus.
Question.7.
Assertion: In diffused reflection, a parallel beam of incident light is reflected in different direction.
Reason: The diffused reflection of light is due to the failure of the laws of reflection.
Ans.7. (c)
Diffuse reflection is caused by the roughness (or irregularities) in the reflecting surface of an object. The laws of reflection are valid at each point even on the rough surface of an object.
Question.8.
Assertion: The image of a virtual object formed by a thin converging lens is always real.
Reason: In the case of a thin lens, \frac{1}{v}- \frac{1}{u}= \frac{1}{f}
Ans.8. (b)
For virtual object
u=+x , F= +ƒ
Therefore,
\frac{1}{v} – \frac{1}{u}= \frac{1}{F}
⇒ \frac{1}{v} – \frac{1}{x}= \frac{1}{f}
⇒ \frac{1}{v} – \frac{1}{f}= \frac{1}{x}
So, v > 0 , it means image is real.
Question.9.
Assertion: In the case of concave mirror, the minimum distance between real object and its real image is zero.
Reason: If concave mirror forms virtual image of real object, the image is magnified.
Ans.9. (b)
If object is placed at centre of curvature of concave mirror, its image is at the centre of curvature. Thus, minimum distance between object and its real image is zero. If object is between pole and focus of concave mirror, its image is virtual and magnified.
Question.10.
Assertion: The size of the mirror affect the nature of the image.
Reason: Small mirrors always form virtual images.
Ans.10. (d)
The size of the image does not affect the nature of the image except that a bigger image as it gathers more light rays due to wider aperture.
Question.11.
Assertion: Keeping a point object fixed, if a plane mirror is moved, the image will also move.
Reason: In case of a plane mirror, distance of object and its image is equal from any point on the mirror.
Ans.11. (a)
The image formed in a plane mirror is at the same distance behind the mirror as the object is in the front of the mirror. Image and the object are at equal distances from a plane mirror.
Question.12.
Assertion: A plane mirror neither converges parallel rays of light nor diverges them.
Reason: The focal length of a plane mirror can be considered to be infinite.
Ans.12. (a)
