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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.
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 with respect to 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’.
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
\dfrac{A'B'}{AB'} = \dfrac{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 \\ [5 bp] \dfrac{-h'}{h} = \dfrac{-v}{-u}. or \dfrac{h'}{h} = -\dfrac{v}{u} \\[5 bp] Thus, The magnification of image, we have
Magnification, m = \dfrac{h'}{h} = -\dfrac{v}{u}.
Explanation:
Height of object, h_1 = + 10 cm \\
Focal length, f = + 12 cm
Object distance, u = - 18 cm
From the lens formula,
\\[4.5 bp] \dfrac{1}{v} – \dfrac{1}{u} = \dfrac{1}{f}\\ [4.5 bp] \dfrac{1}{v} – \dfrac{1}{-18} = \dfrac{1}{12} \\[4.5 bp]
\dfrac{1}{v} + \dfrac{1}{18} = \dfrac{1}{12} \\ [4.5 bp]
\dfrac{1}{v} = \dfrac{1}{12} -\dfrac{1}{18}\\[4.5 bp]
\dfrac{1}{v} = \dfrac{3-2}{36} = \dfrac{1}{36}\\[4.5 bp]
v = 36\space cm\\[4.5 bp]
\text{Magnification, m =} \dfrac{v}{u} = \dfrac{36}{-18} = -2 \\[4.5 bp]
Size of the image,\\[4.5 bp] m = \dfrac{h₂}{h₁}
\\h_2 = m × h₁\\ h_2 = −2×10 = − 20 cm \\[4.5 bp]
The image is formed at a distance of 36 cm from the lens.The image is real, inverted, and magnified.
The height of the image is 20 cm.
Chapter No. | Chapter Name |
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Chapter 1 | Chemical Reactions and Equations |
Chapter 2 | Acid, Bases and Salts |
Chapter 3 | Metals and Non-Metals |
Chapter 4 | Carbon and its Compounds |
Chapter 5 | Life Processes |
Chapter 6 | Control and Coordination |
Chapter 7 | How do Organisms Reproduce |
Chapter 8 | Heredity |
Chapter 9 | Light : Reflection and Refraction |
Chapter 10 | The Human Eye and the Colourful world |
Chapter 11 | Electricity |
Chapter 12 | Magnetic Effects of Electric Current |
Chapter 13 | Our Environment |
Chapter Wise Important Questions for CBSE Board Class 10 Science |
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Chemical Reactions and Equations |
Acid, Bases and Salts |
Metals and Non-Metals |
Carbon and its Compounds |
Life Processes |
Control and Coordination |
How do Organisms Reproduce |
Heredity |
Light : Reflection and Refraction |
The Human Eye and the Colourful world |
Electricity |
Magnetic Effects of Electric Current |
Our Environment |
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