The correct statement among the following related to the concave lens is
a.
converges the light rays
b.
diverges the light rays
Correct Answer
c.
forms inverted image
d.
forms real image.
Step-by-Step AI Explanation
Verified Method
A concave lens is a diverging lens, meaning it causes parallel rays of light passing through it to spread out (diverge). Option A is incorrect because converging is the property of a convex lens. Options C and D are generally incorrect because a concave lens always forms virtual, erect, and diminished images for all positions of the object.
Q2mcq1 mark
The SI unit of resistivity is
a.
ohm
b.
volt
c.
watt
d.
ohm-metre.
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Q3short answer1 mark
Calculate the power of convex lens with a focal length of $+ 0\cdot5$ m.
Step-by-Step AI Explanation
Verified Method
The power ($P$) of a lens is given by the formula $P = \frac{1}{f}$, where $f$ is the focal length in meters. Given $f = +0.5\text{ m}$, the power is $P = \frac{1}{0.5} = +2.0\text{ D}$.
Q4short answer1 mark
What are the reasons for occurring overload in an electric circuit ?
Step-by-Step AI Explanation
Verified Method
Overloading occurs in an electric circuit due to two main reasons: 1) Accidental connection of live wire and neutral wire (short-circuiting), which leads to a massive flow of current due to very low resistance. 2) Connecting too many electrical appliances to a single socket, which exceeds the current-carrying capacity of the circuit wiring.
Q5short answer1 mark
What is a solar cell ?
Step-by-Step AI Explanation
Verified Method
A solar cell is a device that converts solar energy (light energy) directly into electrical energy. It is typically made from semiconductor materials like silicon.
Q6short answer2 marks
An electric bulb with a resistance of $50\ \Omega$ is connected to 10 V battery in an electric circuit. Calculate the electric current flowing through the electric bulb and electric power of the bulb.
Step-by-Step AI Explanation
Verified Method
Given: Resistance $R = 50\ \Omega$, Potential difference $V = 10\text{ V}$.
1) To calculate current ($I$): Using Ohm's Law, $I = \frac{V}{R} = \frac{10}{50} = 0.2\text{ A}$.
2) To calculate power ($P$): Using $P = V \times I = 10\text{ V} \times 0.2\text{ A} = 2\text{ W}$.
Q7short answer2 marks
Draw the diagram of a simple electric motor and label ‘Split rings’ ?
Step-by-Step AI Explanation
Verified Method
The simple electric motor consists of a rectangular coil $ABCD$ placed between the poles of a strong magnet, connected to a battery through a commutator consisting of two half-rings (split rings) $P$ and $Q$. The split rings allow the current in the coil to reverse every half rotation. (For the diagram, draw a rectangular loop between magnetic poles $N$ and $S$, with the two ends of the coil connected to two semicircular rings $P$ and $Q$ that rotate with the coil, and label $P$ and $Q$ as the split rings).
Q8short answer2 marks
Write any two limitations of producing electricity from wind energy.
Step-by-Step AI Explanation
Verified Method
Two limitations of wind energy are: 1) Wind farms can only be established at specific locations where wind speed is sufficiently high and consistent throughout the year. 2) The initial cost of setting up wind energy generators and the associated infrastructure is very high.
Q9short answer3 marks
a) State the two laws of refraction of light.
b) "The refractive index of diamond is $2\cdot42$." Write the meaning of this statement.
Step-by-Step AI Explanation
Verified Method
a) The two laws of refraction of light are: 1. The incident ray, the refracted ray and the normal to the interface of two transparent media at the point of incidence, all lie in the same plane. 2. The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for the light of a given colour and for the given pair of media (Snell's Law): $$\frac{\sin i}{\sin r} = \text{constant}$$.
b) The statement 'The refractive index of diamond is $2.42$' means that the ratio of the speed of light in air to the speed of light in diamond is $2.42$. It implies that light travels $2.42$ times slower in diamond than it does in a vacuum.
Q10long answer3 marks
Draw the ray diagram of image formation when the object is kept at $2F_1$ of the convex lens. With the help of the ray diagram, mention the position and nature of the image formed. [$F_1$ : Principal focus of the lens]
OR
Draw the ray diagram of image formation when the object is kept between C and F of the concave mirror. With the help of the ray diagram mention the position and the nature of the image formed. [$F$ : Principal focus of the mirror, C : Centre of curvature of mirror]
Step-by-Step AI Explanation
Verified Method
For an object kept at $2F_1$ of a convex lens: 1. Position of image: The image is formed at $2F_2$ on the other side of the lens. 2. Nature of image: The image is real, inverted, and of the same size as the object. (Ray diagram: Rays from the top of the object parallel to the principal axis pass through $F_2$; rays passing through the optical center $O$ continue undeviated; they intersect at $2F_2$.)
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a) Write any four uses of concave mirror.
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b) Why are the alloys like nichrome used in electrical heating devices ?
OR
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