Q.By drawing a ray diagram, explain the formation of image in a compound microscope. Establish the formula for magnifying power for it. OR In a circuit, the equation for alternative voltage V is represented by $V = 40 \sin (100 \pi t)$ volt. Here $t$ is in seconds. Draw the time-voltage ($t$-$V$) graph with proper scale for one cycle. Calculate the root mean square value of voltage.

Showing the 12 most recent of 15 on this concept.

1. CBSE 2026Set A1 markMCQ
   Q.When the tube length of microscope is increased, its magnifying power (A) increases (B) decreases (C) becomes zero (D) remains unchanged

   ›Reveal solutionSolution

   The magnifying power of a compound microscope is proportional to the tube length, so increasing L increases the magnification.

   For a compound microscope the magnifying power is approximately

   $M = \frac{L}{f_o}\cdot\frac{D}{f_e}$ …

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2. CBSE 2026Set ANNUAL1 markMCQ
   Q.The image formed by a simple microscope is

   (a) imaginary and erect

   (b) imaginary and inverted

   (c) real and erect

   (d) real and inverted

   ›Reveal solutionSolution

   A simple microscope is just a convex lens used with the object inside its focal length, which always produces a virtual, erect, magnified image.

   A simple microscope is a single convex lens. When the object is placed BETWEEN the lens and its focal point (object distance less than f), the convex lens produces an image that is on the SAME side as the object, virtual (cannot be caught on a screen - here called 'imaginary'), erect (same orienta …

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3. CBSE 2026Set ANNUAL1 markMCQ
   Q.Assertion (A): The magnifying power of a simple microscope is inversely proportional to the focal length of the lens. Reason (R): Power of a lens is inversely proportional to the focal length.

   (a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

   (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).

   (c) Assertion (A) is true, but Reason (R) is false.

   (d) Assertion (A) and Reason (R) both are false.

   ›Reveal solutionSolution

   Both statements are true, and since $M = D/f = D\times P$, the fact that power $P \propto 1/f$ directly explains why magnifying power is inversely proportional to $f$.

   For a simple microscope, magnifying power (image at infinity) is $M = \dfrac{D}{f}$, where $D$ is the least distance of distinct vision. This can be rewritten as $M = D \times \dfrac{1}{f} = D \times P$, where $P = \dfrac{1}{f}$ is the power of the lens. So $M$ is directly proportional to the lens's power, and since power is inver …

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4. CBSE 2025Set X11 markMCQ
   Q.Final image of a real object formed by a compound microscope is __________ with respect to the object.

   (a) real, inverted and magnified

   (b) virtual, erect and magnified

   (c) virtual, erect and diminished

   (d) virtual, inverted and magnified

   ›Reveal solutionSolution

   (d) virtual, inverted and magnified. In a compound microscope the objective forms a real, inverted, magnified image, which acts as the object for the eyepiece. The eyepiece then forms a final imag …

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5. CBSE 2025Set IMPROVEMENT1 mark
   Q.Write the formula for the total magnification of a compound microscope when the final image is formed at infinity.

   ›Reveal solutionSolution

   For a compound microscope with the final image at infinity, the total magnifying power is the product of the objective's linear magnification and the eyepiece's angular magnification.

   In a compound microscope, the objective lens forms a real, magnified image of the object; this image acts as the object for the eyepiece, which forms the final image. When the eyepiece is adjusted so that the final image is formed at infinity (normal/relaxed-eye viewing), the total magnifying power is:

   $M = m_o \times m_e = \dfrac{L}{f_o}\times\dfrac{D}{f_e}$ …

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6. CBSE 2024Set A1 markMCQ
   Q.Image formed in compound microscope is (A) real and erect (B) real and inverted (C) virtual and inverted (D) virtual and erect

   ›Reveal solutionSolution

   A compound microscope forms a final image that is virtual, magnified and inverted → option (C).

   In a compound microscope the objective lens first forms a real, inverted, magnified image of the object. This intermediate image acts as the object for the eyepiece, which is used as a simple magnifier and forms the **final image that is virtual, further magnifie …

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7. CBSE 2024Set ANNUAL1 markMCQ
   Q.If the magnification of objective and eyepiece in a compound microscope is 'm_o' and 'm_e' respectively, then the total magnifying power (m) of the microscope will be -

   (a) m_o + m_e

   (b) m_o - m_e

   (c) m_o . m_e

   (d) m_o / m_e

   ›Reveal solutionSolution

   In a compound microscope, the objective forms a magnified real image which the eyepiece further magnifies, so the two magnifications multiply.

   In a compound microscope, the objective lens forms a real, magnified, inverted image of the object with magnification $m_o$. This image acts as the object for the eyepiece, which further magnifies it (acting like a simple magnifier) with magnification $m_e$.

   …

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8. CBSE 2023Set ANNUAL1 markMCQ
   Q.The image formed by a simple microscope is

   (1) imaginary and erect

   (2) imaginary and inverted

   (3) real and erect

   (4) real and inverted

   ›Reveal solutionSolution

   A simple microscope is a single converging lens used with the object inside its focal length, producing a virtual, erect, magnified image.

   When the object is placed within the focal length of a convex lens, the emergent rays diverge, and appear to come from a point behind the lens on the same side as the object …

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9. CBSE 2022Set I1 markMCQ
   Q.Magnifying power of simple microscope is (A) M = 1 - D/f (B) M = 1 + D/f (C) M = 1 - f/D (D) M = 1 + f/D

   ›Reveal solutionSolution

   Simple microscope (image at near point): $M = 1 + \dfrac{D}{f}$.

   A simple microscope is a single convex lens of focal length $f$ used as a magnifier. When the final image is formed at the least distance of distinct vision $D$ ($\approx 25$ cm), the angular magnification is

   $M = 1 + \frac{D}{f}.$

   …

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10. CBSE 2022Set HE2171 markMCQ
    Q.The focal length of eye in compound microscope ________ the focal length of the objective.

    (i) is less than

    (ii) is more than

    (iii) is equal

    (iv) None of these

    ›Reveal solutionSolution

    The eyepiece focal length of a compound microscope is greater than the objective's focal length.

    In a compound microscope, the objective lens is placed very close to the small object and has a very small focal length $f_o$, so that it forms a highly magnified real, inverted, enlarged image close to the eyepiece. The eyepiece then acts like a simple magnifier and further magnifies this image; it is given a comparatively larger focal length $f_e$ so it can view the intermediate image comfortably while still giving good magnification. …

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11. CBSE 2022Set HE2171 mark
    Q.Match the following. Column A item: 'Magnifying power of Compound Microscope'. Choose its matching entry from Column B:

    (a) (1 - D/f)

    (b) Hertz

    (c) Electromagnetic induction

    (d) (-v0/u0)(1 + D/fe)

    (e) V.I.

    (f) Hershel

    (g) Instrument of measuring current

    (h) Instrument of measuring potential

    (i) Polarisation of light

    (j) Unit of energy

    ›Reveal solutionSolution

    The magnifying power of a compound microscope is $M = \left(-\dfrac{v_0}{u_0}\right)\left(1+\dfrac{D}{f_e}\right)$, matching option (d).

    The overall magnification of a compound microscope is the product of the linear magnification produced by the objective, $m_o = v_0/u_0$, and the angular magnification produced by the eyepiece used as a simple magnifier with the final image at the near point, $m_e = 1 + D/f_e$ (D = least distance of distinct vision). This gives t …

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12. CBSE 2021Set A1 markMCQ
    Q.The image formed by simple microscope is (A) Virtual and erect (B) Virtual and inverted (C) Real and erect (D) Real and inverted

    ›Reveal solutionSolution

    A simple microscope produces a virtual, erect, magnified image.

    A simple microscope is a single convex lens used as a magnifying glass. The object is placed within the focal length (between the lens and its focus), so the lens forms an image that is virtual, erect, and enlarged, on the same side as the object (typically at the n …

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