Light : Reflection and Refraction

Important Questions

Here are some critical Chapter 9 Light : Reflection and RefractionProblems for Class 10 Science. These inquiries are intended to aid students in studying for and performing well on the CBSE Class 10 Science Examination 2023–24. Students can clear up their concerns and be ready for the exams by practising different types of questions. By answering these questions, you'll increase your confidence while also sharpening your problem-solving abilities

Tables of Content

Chapter 9, "Light: Reflection and Refraction," in Class 10 Science, delves into the captivating phenomenon of light. It encompasses the reflection of light, exploring how it interacts with surfaces, and delves into the intriguing world of spherical mirrors. Additionally, this chapter explores the concept of light refraction, shedding light on how light changes its path when it traverses from one medium to another, unraveling the mysteries of optics and vision.

(b) A concave lens of focal length 50 cm.

(c) A convex lens of focal length 5 cm.

(d) A concave lens of focal length 5 cm.

**Ans**. (c)

**Explanation:**A convex lens with a short focal length (5 cm) is used to read small letters and to see the magnified image of a small object.

(b) less than unity

(c) equal to unit

(d) zero

**Ans**. (a)

**Explanation:**As the light ray when travelled from medium A to medium B, then they bend towards the normal which means that medium B has higher refractive index and less speed of light with respect to medium A, So, refractive index of medium B w.r.t. medium A will be greater than unity.

**Explanation:**The refractive index for the light going from medium ‘1’ to medium ‘2’ is equal to the reciprocal of the refractive index for light going from medium ‘2’ to medium ‘1’.

1

**Explanation:**Consider the formation of the image A′B′ of an object AB by a concave mirror. As shown in the given figure, the right angled triangles ABP and A′B′P are similar triangles, hence

\(\frac{A'B'}{AB} = \frac{A'B'}{AB}\)

As per sign convention followed, PB = - u, PB’ = - v, AB = size of the object = + h and A'B' = size of the image = - h’. Hence, we have

\(\frac{-h'}{h} = \frac{-v}{u} or \frac{-h'}{h} = - \frac{v}{u}\)

Thus, by definition of magnification of image, we have

Magnification, m =\(\frac{h'}{h} = \frac{v}{u}\).

**Explanation:**Height of object, h

Focal length, f = + 12 cm

Object distance, u = - 18 cm

From the lens formula,

\(\frac{1}{v} - \frac{1}{u} = \frac{1}{f}\)

⇒ \(\frac{1}{v} - \frac{1}{-18} = \frac{1}{12}\)

⇒ \(\frac{1}{v} + \frac{1}{18} = \frac{1}{12}\)

⇒ \(\frac{1}{v} = \frac{1}{12} - \frac{1}{18}\)

⇒ \(\frac{1}{v} = \frac{3-2}{36} = \frac{1}{36}\)

⇒ v = 36 cm

⇒ Magnification, m = \(\frac{v}{u} = \frac{36}{-18} = -2\)

The position of the image formed is at a distance of 36 cm from the convex lens.

oswal.io offers a thorough set of questions for learning the topic in a better way if you're looking to further practise and improve your grasp of the concepts covered in the chapter.

**Ans: **Light rays that are parallel to the principal axis of a concave mirror converge at a specific point on its principal axis after reflecting from the mirror. This point is called the principal focus of the concave mirror.

**Ans: ** Radius of curvature (R) = 20 cm

Radius of curvature of the spherical mirror = 2 × Focal length (f)

R = 2f

f= R/2 = 20 / 2 = 10

Therefore, the focal length of the spherical mirror is 10 cm.

**Ans: **The mirror that can give an erect and enlarged image of an object is a Concave Mirror.

**Ans:** A convex mirror is preferred as a rear-view mirror in cars and vehicles as it gives a wider field of view, which helps the driver see most of the traffic behind him. Convex mirrors always form an erect, virtual, and diminished image of the objects placed in front of it.

**Ans:** The light ray bends towards the normal. When a light ray enters from an optically rarer medium (which has a low refractive index) to an optically denser medium (which has a high refractive index), its speed slows down and bends towards the normal. As water is optically denser than air, a ray of light entering from air into water will bend towards the normal.

Chemical Reactions and

EquationsAcid, Bases and SaltsMetals and Non-MetalsCarbon and its CompoundsLife ProcessesControl and CoordinationHow do Organisms ReproduceHeredityLight : Reflection and RefractionThe Human Eye and the

Colourful worldElectricityMagnetic Effects of Electric

CurrentOur Environment

EquationsAcid, Bases and SaltsMetals and Non-MetalsCarbon and its CompoundsLife ProcessesControl and CoordinationHow do Organisms ReproduceHeredityLight : Reflection and RefractionThe Human Eye and the

Colourful worldElectricityMagnetic Effects of Electric

CurrentOur Environment