To get virtual and erect image by a convex lens, an object is to be placed
a.
beyond $2F_1$
b.
between $F_1$ and $2F_1$
c.
at focus $F_1$
d.
between focus $F_1$ and optical centre O
Correct Answer
Step-by-Step AI Explanation
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For a convex lens, a virtual and erect image is formed only when the object is placed between the optical centre (O) and the principal focus (F1). Option (a) results in a diminished, real, and inverted image. Option (b) results in a real, inverted, and magnified image. Option (c) results in a real, inverted, and highly magnified image formed at infinity.
Q2mcq1 mark
The colour that is least scattered by fog and smoke is
a.
orange
b.
blue
c.
red
Correct Answer
d.
violet
Step-by-Step AI Explanation
Verified Method
According to Rayleigh's law of scattering, the intensity of scattered light is inversely proportional to the fourth power of its wavelength ($\lambda^{-4}$). Red light has the longest wavelength in the visible spectrum and therefore scatters the least. Blue and violet light have much shorter wavelengths and scatter significantly more.
Q3mcq1 mark
The magnetic field inside a long straight solenoid carrying current
a.
is the same at all points
Correct Answer
b.
is zero
c.
decreases as we move towards its end
d.
increases as we move towards its end
Step-by-Step AI Explanation
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A long straight solenoid produces a magnetic field that is uniform (same in both magnitude and direction) at all points inside, resembling the field of a bar magnet. Outside the solenoid, the field is negligible.
Q4mcq1 mark
Identify the wrong statement among the following statements regarding refraction and dispersion of light.
a.
Stars twinkle
b.
Sky appears blue to an astronaut flying at very high altitudes
Correct Answer
c.
The sun is visible to us about two minutes before the actual sunrise
d.
Planets do not twinkle
Step-by-Step AI Explanation
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The sky appears dark to an astronaut at high altitudes because there is no atmosphere at those heights to scatter sunlight. Blue light is scattered by the atmosphere, which is why the sky appears blue from the Earth's surface. Therefore, stating the sky appears blue at high altitudes is the wrong statement. Options (a), (c), and (d) are all correct phenomena related to atmospheric refraction.
Q5short answer1 mark
Write the symbols of the following components used in an electric circuit.
i) Wires crossing without joining
ii) Voltmeter
Step-by-Step AI Explanation
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i) Wires crossing without joining: Represented by two lines crossing where one has a small semi-circular hump over the other.
ii) Voltmeter: Represented by a circle with the letter 'V' inside, having two connecting terminals.
Q6short answer1 mark
Observe the below figure showing the refraction of light through a glass prism. Name the angle represented as $x$ and give reason for the formation of that angle.
Step-by-Step AI Explanation
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The angle represented as $x$ is the Angle of Deviation ($\delta$). It is formed because light rays undergo refraction twice (at the first and second surfaces of the prism) while passing through the glass prism. The ray of light bends towards the base of the prism, causing the emergent ray to deviate from the direction of the incident ray.
Q7short answer2 marks
Observe the given figure : If the key connected to Coil-2 is plugged, in which of the other two coils more current is induced ? Why ?
Step-by-Step AI Explanation
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More current is induced in Coil-1. This is because Coil-1 is physically closer to the central solenoid (Coil-2) where the current is being switched on. The magnetic flux linkage (change in magnetic field lines) is stronger for the adjacent coil, resulting in a higher induced EMF and thus more induced current compared to the coil further away.
Q8short answer2 marks
State two laws of reflection of light.
Step-by-Step AI Explanation
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The two laws of reflection of light are:
1. The angle of incidence is equal to the angle of reflection ($\angle i = \angle r$).
2. The incident ray, the reflected ray, and the normal to the surface at the point of incidence all lie in the same plane.
Q9short answer3 marks
A concave lens has focal length of 25 cm. At what distance should the object from the lens be placed so that it forms an image at 20 cm from the lens ? Find the magnification of the image produced by the lens.
Step-by-Step AI Explanation
Verified Method
Given: Focal length of concave lens $f = -25 \text{ cm}$, Image distance $v = -20 \text{ cm}$ (since the image is virtual). By the lens formula: $$\frac{1}{f} = \frac{1}{v} - \frac{1}{u}$$ $$\frac{1}{-25} = \frac{1}{-20} - \frac{1}{u}$$ $$\frac{1}{u} = \frac{1}{25} - \frac{1}{20} = \frac{4-5}{100} = -\frac{1}{100}$$ So, $u = -100 \text{ cm}$. The object should be placed 100 cm from the lens. Magnification $m = \frac{v}{u} = \frac{-20}{-100} = 0.2$.
Q10short answer3 marks
Draw the ray diagrams that show :
i) Near point of hypermetropic eye
ii) Hypermetropic eye
iii) Correction for hypermetropic eye.
Step-by-Step AI Explanation
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i) Near point of hypermetropic eye: The near point is farther away than the normal 25 cm. ii) Hypermetropic eye: Light rays from a nearby object (at 25 cm) focus behind the retina because the eyeball is too short or the lens is too weak. iii) Correction for hypermetropic eye: A convex lens is used to converge the rays before they enter the eye, shifting the image onto the retina.
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a) Mention the function of digester present in bio-gas plant.
b) Mention four properties to support that the bio-gas is an excellent fuel.
OR
a) Mention any four properties of a good source of energy.
b) Mention the principal advantages of solar cells.
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a) Explain an experiment of drawing magnetic field lines around a bar magnet with the help of a compass needle.
b) Mention two properties of magnetic field lines.
OR
a) Explain an experiment to show that a current carrying conductor experiences the force in a magnetic field.
b) How is a simple electric motor converted into a commercial motor ?
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a) Explain an experiment of drawing magnetic field lines around a bar magnet with the help of a compass needle.
b) Mention two properties of magnetic field lines.
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a) What is resistance of a conductor ? On what factors does the resistance of a conductor depend?
b) It is advantageous to connect electrical devices in parallel instead of connecting them in series. Why ? Explain.
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Aluminium, Iron, Magnesium and Zinc metals reacted with dilute hydrochloric acid. The series that indicates decreasing order of reactivity of these metals is
a.
Mg > Al > Zn > Fe
b.
Al > Mg > Fe > Zn
c.
Fe > Zn > Al > Mg
d.
Fe > Mg > Zn > Al
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a) Explain an experiment to show that a current carrying conductor experiences the force in a magnetic field.
b) How is a simple electric motor converted into a commercial motor?
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a) What is the chemical formula of bleaching powder? Write any two uses of this salt.
b) Name the acid present in the following substances.
i) Curd
ii) Gastric juice
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Observe the given part of the modern periodic table and answer the following questions:
| Elements | p | q | r | s |
|---|---|---|---|---|
| Atomic No. | 4 | 5 | 3 | 7 |
i) Find the valence electrons of the elements ‘q’ and ‘r’.
ii) Which element has larger atomic size and why?
iii) Find the most electronegative element and give reason.
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a) If the molecular formula of first member of a homologous series is $C_{2}H_{2}$, then write the names and the molecular formulae of the next two members of the same series.
b) Generally vegetable oils are subjected to hydrogenation. Why?
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a) Write the balanced chemical equations for the following reactions:
i) Calcium carbonate on heating produces calcium oxide and carbon dioxide.
ii) Burning of natural gas (methane) produces carbon dioxide and water.
b) Give reason:
i) Articles made of copper lose their shiny surface when exposed to air.
ii) An iron nail placed in copper sulphate solution slowly turns to brown colour.
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The electronic configuration of the three elements x, y and z are 2,8,7 ; 2,8,8 and 2,8,1 respectively.
i) Which element is the most electropositive and why?
ii) Which element has zero valency and why?
iii) Predict the type of the chemical bond that forms when ‘x’ and ‘z’ elements react each other and mention the reason.
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In an aquatic eco-system the organisms such as fishes, birds, insect larvae and diatoms are found. Construct a food chain using these organisms. If 10 calories of energy is available to the tertiary consumers in this food chain, what amount of energy was produced in the first trophic level ?
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If the molecular formula of first member of a homologous series is $C_2H_2$, then write the names and the molecular formulae of the next two members of the same series.
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Red flowering (RR) 4 O’clock plant is crossed with white flowering (WW) 4 O’clock plant. There are 25% red flowering, 25% white flowering and 50% hybrids are obtained in $F_2$ generation. Then, i) What are the characteristics of plants of $F_1$ generation ?
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Red flowering (RR) 4 O’clock plant is crossed with white flowering (WW) 4 O’clock plant. There are 25% red flowering, 25% white flowering and 50% hybrids are obtained in $F_2$ generation. Then, ii) Show the results of $F_2$ generation with the help of a checker board and mention the genotypic ratio.
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Red flowering (RR) 4 O’clock plant is crossed with white flowering (WW) 4 O’clock plant. There are 25% red flowering, 25% white flowering and 50% hybrids are obtained in $F_2$ generation. Then, iii) Determine the trait that can be considered either as ‘dominant’ or ‘recessive’ by analysing the results of both $F_1$ and $F_2$ generations.
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Read, analyse the given situations and answer the questions given below: Situation 1: Many vegetables and fruits are now available in different colours and sizes. Situation 2: The colour of the wings in the population of Drosophila insects is turning to black due to the increase of carbon in some industrial areas. i) In which of the situations the genetic drift happens fastly and why ?
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