Light – Reflection and Refraction
- A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Power of lens, P= 1/f P= 1.5D f= 1/1.5 = 10/15 = 0.66 m A convex lens has a positive focal length. Hence, it is a convex lens or a convergin... 1
- Find the focal length of a lens of power -2.0 D. What type of lens is this? Power of lens, P= 1/f P= -2D f= -1/2 = -0.5 m A concave lens has a negative focal length. Hence, it is a concave lens. 1
- An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. https://www.youtube.com/watch?v=meqKmlYN_p8&ab_channel=2Piclasses An object of size 7.0 cm is placed at 27 cm in front of a concave mirror o... 2
- An object 5 cm is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. https://youtu.be/Axatke6lD44 2
- The magnification produced by a plane mirror is +1. What does this mean? The positive sign means image formed by a plane mirror is virtual and erect. Since the magnification is 1 it means that the size of the imag... 1
- An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image. https://yo... 2
- A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram. h... 2
- An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size a... 2
- One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? The convex lens will form complete image of an object, even if its one half is covered with black paper. It can be understood by the followi... 1
- Name the type of mirror used in the following situations. (a) Headlights of a car a) Concave Mirror: This is because concave mirrors can produce powerful parallel beam of light when the light source is placed at their prin... 1
- We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. Range of the distance of the object = 0 to 15 cm from the pole of the mirror. Nature of the image = virtual, erect and larger than the objec... 1
- Which of the following lenses would you prefer to use while reading small letters found in a dictionary? c) A convex lens of focal length 5 cm 2
- No matter how far you stand from a mirror, your image appears erect. The mirror is likely to be d) either plane or convex 2
- A spherical mirror and a thin spherical lens have each a focal length of -15 cm. The mirror and the lens are likely to b a) both concave 2
- Where should an object be placed in front of a convex lens to get a real image of the size of the object? b) At twice the focal length 2
- The image formed by a concave mirror is observed to be virtual, erect and larger than the object. d) Between the pole of the mirror and its principal focus. 2
- Which one of the following materials cannot be used to make a lens? (a) Water (b) Glass (c) Plastic (d) Clay Correct option is d) Clay 2
- Find the power of a concave lens of focal length 2 m. Focal length of concave lens, f = 2 mPower of lens, P= 1/f = 1/(-2)= -0.5D 1
- A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it Since the image is real and same size. The position of image should be at 2F. It is given that the image of the needle is formed at a distan... 1
- Define 1 dioptre of power of a lens. The SI unit of power of lens is dioptre which is denoted by the letter D. 1 dioptre is defined as the power of a lens of focal length 1 metr... 1
- The refractive index of diamond is 2.42. What is the meaning of this statement? The refractive index of diamond is 2.42. This means that the speed of light in diamond will reduce by a factor of 2.42 as compared to its sp... 1
- You are given kerosene, turpentine and water. In which of these does the light travel fastest? In water light travel faster as compare to kerosene and turpentine because the refractive index of water is lower than that of kerosene and... 1
- Find out, from Table, the medium having highest optical density. Also find the medium with lowest optical density. Highest optical density = Diamond Lowest optical density = Air Optical density of a medium is directly related with the refractive index of... 1
- Light enters from air to glass having refractive index 1.50. What is the speed of light in the glass? Refractive index of a medium, n_m = Speed of light in vacuum/Speed of light in the medium Speed of light in vacuum, c = 3 × 10⁸ ms⁻¹ Refract... 1