कृषि, पशु र वन विज्ञान प्रवेश
कृषि, पशु र वन विज्ञान प्रवेश
Agriculture, Veterinary & Forestry Entrance · २,४९३ प्रश्न
२,४९३ प्रश्न उपलब्ध। मोड छान्नुहोस्:
कृषि/वन प्रवेश: प्रश्न र उत्तर
सही लागेको विकल्पमा थिच्नुहोस्। सही भए हरियो, गलत भए रातो देखिन्छ; ३ सेकेन्डपछि सही उत्तर र व्याख्या देखिन्छ।
सही: ० / ०
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Two thin lenses of power +2 D and −1 D are placed in contact. The focal length of the combination is:
सही उत्तर: घ) 100 cm
Net power P = +2 − 1 = +1 D, so f = 1/P = 1 m = 100 cm (converging). 33.3 cm would come from adding the magnitudes to get 3 D.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An object is placed beyond 2F in front of a convex lens. The image formed is:
सही उत्तर: घ) Real, inverted and diminished, between F and 2F
For an object beyond 2F, a convex lens forms a real, inverted, smaller image between F and 2F on the other side. A same-size image forms only when the object is at 2F.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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When white light passes through a prism, the colour that deviates the most is:
सही उत्तर: क) Violet
Refractive index of glass is highest for violet (shortest wavelength), so violet bends the most and red the least.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The sky appears blue because of:
सही उत्तर: ग) Scattering of light
Air molecules scatter shorter wavelengths (blue) much more than longer ones (Rayleigh scattering ∝ 1/λ⁴), so scattered blue light reaches us from all directions.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Total internal reflection occurs when light travels from a:
सही उत्तर: ग) Denser to rarer medium at an angle of incidence greater than the critical angle
Both conditions are needed: light must go from optically denser to rarer, and the angle of incidence must exceed the critical angle.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The refractive index of glass is 1.5. If the speed of light in vacuum is 3 × 10⁸ m/s, its speed in glass is:
सही उत्तर: क) 2 × 10⁸ m/s
n = c/v, so v = c/n = 3 × 10⁸/1.5 = 2 × 10⁸ m/s. Light is slower in a denser medium, so a value larger than c is impossible.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An object is placed 20 cm in front of a concave mirror of focal length 10 cm. The image is formed:
सही उत्तर: घ) 20 cm in front of the mirror
The object is at C (2f = 20 cm), so the image is also at C: real, inverted and the same size. An image at infinity forms only when the object is at the focus.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A pipe closed at one end produces:
सही उत्तर: ख) Only odd harmonics
A closed pipe has a node at the closed end and antinode at the open end, so only odd harmonics (1, 3, 5...) are present. An open pipe produces all harmonics.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Taking the speed of sound as 340 m/s and the persistence of hearing as 0.1 s, the minimum distance of a reflecting surface for a distinct echo is:
सही उत्तर: क) 17 m
Sound must travel to the wall and back in at least 0.1 s: 2d = 340 × 0.1 = 34 m, so d = 17 m. 34 m is the total path, not the distance to the wall.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A sound wave has a frequency of 500 Hz and wavelength 0.68 m. Its speed is:
सही उत्तर: क) 340 m/s
v = fλ = 500 × 0.68 = 340 m/s. Dividing instead of multiplying gives a wrong value of about 735 m/s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
यी अभ्यास प्रश्न हुन्, आधिकारिक प्रश्न होइनन्। पाठ्यक्रम, विज्ञापन र नतिजाका लागि सम्बन्धित निकायको आधिकारिक वेबसाइट हेर्नुहोस्। उत्तरमा गल्ती भेटे प्रश्नमुनिको "टिप्पणी / गल्ती रिपोर्ट" मा लेख्नुहोस्।
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