The process of nitrogen fixation in legumes is performed by which organism?

The correct answer is B: Rhizobium (Nitrogen-fixing bacteria in root nodules). Rhizobium bacteria form symbiotic associations with legume roots, fixing atmospheric N2 into ammonia. The bacteria live in root nodules. This symbiotic relationship is agriculturally significant and frequently tested in competitive exams.

The pH of cell sap in plant cells typically ranges between:

The correct answer is B: 4-6. Plant cell sap is slightly acidic due to organic acids like malic acid and citric acid, maintaining pH between 4-6.

A satellite orbits Earth at radius r with orbital velocity v. If the orbital radius is doubled, what happens to the orbital velocity?

The correct answer is C: It decreases by factor √2. From orbital mechanics: v = √(GM/r). If r becomes 2r, then v_new = √(GM/2r) = v/√2. Velocity decreases by factor √2.

A gas expands against a constant external pressure of 2 atm. The work done by the gas is -500 J. What is the change in volume?

The correct answer is B: 2.47 L. Work done against constant pressure: W = -PΔV. Given W = -500 J and P = 2 atm = 2 × 101325 Pa. ΔV = -W/P = 500/(2 × 101325) ≈ 2.47 × 10⁻³ m³ = 2.47 L.

The refractive index of a medium is 1.5. What is the speed of light in that medium? (c = 3 × 10⁸ m/s)

The correct answer is B: 2 × 10⁸ m/s. Refractive index n = c/v. Therefore, v = c/n = (3 × 10⁸)/1.5 = 2 × 10⁸ m/s.

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Showing 1–2 of 2 questions in Space & Astronomy

Q.1 Easy Space & Astronomy

Which celestial phenomenon occurs when the Moon passes between the Earth and the Sun, blocking the Sun's light and casting a shadow on Earth?

A Solar Eclipse

B Lunar Eclipse

C Penumbral Eclipse

D Annular Eclipse

Correct Answer: A. Solar Eclipse

Explanation:

A solar eclipse happens when the Moon's orbit places it directly between Earth and the Sun, creating a shadow on Earth's surface.

This is distinct from a lunar eclipse where Earth blocks sunlight from reaching the Moon, and from penumbral or annular eclipses which are specific types with different characteristics.

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Q.2 Easy Space & Astronomy

Planet closest to Sun?

A Venus

B Mercury

C Earth

D Mars

Correct Answer: B. Mercury

Explanation:

Mercury is closest to Sun.

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