#neet
- Hypersecretion of Growth Hormone in adults does not cause further increase in height, because : Answer: 1. Epiphyseal plates close after adolescence. Height increases through growth at the epiphyseal plates of long bones. After adolesce... 1
- Plants which produce characteristic pneumatophores and show vivipary belong to : Answer: 1. Halophytes Mangrove plants live in saline, waterlogged soil. They have pneumatophores (breathing roots) and show vivipary (seed g... 1
- Asymptote in a logistic growth curve is obtained when : Answer: 1. K = N In the logistic growth curve the upper asymptote is reached when the population size N equals the carrying capacity K , so... 1
- Good vision depends on adequate intake of carotene-rich food.Select the best option from the following statements.(a) Vitamin A derivatives are formed from carotene.(b) The photopigments are embedded in the membrane discs of the inner segment.(c) Ret… Answer: 1. (a), (c) and (d) Go statement by statement. (a) True: vitamin A derivatives form from carotene. (b) False: photopigments lie in t... 1
- Artificial selection to obtain cows yielding higher milk output represents : Answer: 1. directional as it pushes the mean of the character in one direction. Selecting cows for higher milk yield moves the mean of the t... 1
- Frog's heart when taken out of the body continues to beat for sometime.Select the best option from the following statements.(a) Frog is a poikilotherm.(b) Frog does not have any coronary circulation.(c) Heart is "myogenic" in nature.(d) Heart is auto… Answer: 3. (c) and (d) An isolated frog heart keeps beating because it is myogenic (the beat starts in the heart muscle itself) and autoexci... 1
- Which one from those given below is the period for Mendel's hybridization experiments ? Answer: 4. 1856 - 1863 Mendel carried out his hybridization experiments on garden pea from 1856 to 1863. He published the results in 1866. 1
- Two astronauts are floating in gravitational free space after having lost contact with their spaceship. The two will : Answer: 1. move towards each other. Key idea: the only force between the two astronauts is their mutual gravitational attraction. In free sp... 1
- Young's double slit experiment is first performed in air and then in a medium other than air. It is found that 8^th bright fringe in the medium lies where 5^th dark fringe lies in air. The refractive index of the medium is nearly : Answer: 3. 1.78 Key idea: compare fringe positions using bright fringe y_n=nλ D/d and dark fringe y_n=(2n-1)λ D/2d . In air, 5th dark fringe... 1
- In a common emitter transistor amplifier the audio signal voltage across the collector is 3 V. The resistance of collector is 3 kΩ. If current gain is 100 and the base resistance is 2 kΩ, the voltage and power gain of the amplifier is : Answer: 2. 150 and 15000 Key idea: in a common emitter amplifier, voltage gain A_v=βR_C/R_B and power gain =β A_v . A_v=100×3\ kΩ/2\ kΩ=150... 1
- An arrangement of three parallel straight wires placed perpendicular to plane of paper carrying same current 'I' along the same direction is shown in Fig. Magnitude of force per unit length on the middle wire 'B' is given by : Answer: 3. μ₀ i²/√(2)π d Key idea: parallel wires carrying current in the same direction attract each other, each pair giving a force per un... 1
- The de-Broglie wavelength of a neutron in thermal equilibrium with heavy water at a temperature T (Kelvin) and mass m, is : Answer: 1. h/√(3mkT) Key idea: a thermal neutron has average kinetic energy 3/2kT , and λ=h/p=h/√(2mK) . λ=h/√(2m·3/2kT)=h/√(3mkT) . 1
- Radioactive material 'A' has decay constant '8λ' and material 'B' has decay constant 'λ'. Initially they have same number of nuclei. After what time, the ratio of number of nuclei of material 'B' to that 'A' will be 1/e ? Answer: 1. 1/7λ Key idea: N=N₀e^(-λ t) for each material, and take the ratio of the two. N_A=N₀e^(-8λ t) , N_B=N₀e^(-λ t) . Then N_A/N_B=e^(... 1
- The given electrical network is equivalent to : Answer: 2. NOR gate Key idea: trace the logic step by step. First gate is a NOR: output A+B . Second gate is a NOR with both inputs joined,... 1
- The resistance of a wire is 'R' ohm. If it is melted and stretched to 'n' times its original length, its new resistance will be : Answer: 2. n²R Key idea: melting does not change the volume, so Al stays constant. If length becomes nl , area becomes A/n . Resistance R=ρl... 1
- Two cars moving in opposite directions approach each other with speed of 22 m/s and 16.5 m/s respectively. The driver of the first car blows a horn having a frequency 400 Hz. The frequency heard by the driver of the second car is [velocity of sound 3… Answer: 3. 448 Hz Key idea: Doppler effect with source and observer approaching: f'=fv+v_o/v-v_s . f'=400×340+16.5/340-22=400×356.5/318≈448... 1
- In an electromagnetic wave in free space the root mean square value of the electric field is E_rms = 6 V/m. The peak value of the magnetic field is : Answer: 1. 2.83×10⁻⁸ T Key idea: peak value =sqrt2× rms value, and B₀=E₀/c . E₀=6sqrt2=8.49 V/m. B₀=8.49/3×10⁸=2.83×10⁻⁸ T. 1
- Two rods A and B of different materials are welded together as shown in figure. Their thermal conductivities are K_1 and K_2. The thermal conductivity of the composite rod will be : Answer: 4. K₁+K₂/2 Key idea: the two rods are side by side, so heat flows through them in parallel, and the conductances add. Let each rod h... 1
- Coconut fruit is a : Answer: 4. Drupe Coconut is a drupe: a one-seeded fruit developed from a superior ovary. It has a fibrous mesocarp (husk) and a hard stony e... 1
- Attractants and rewards are required for : Answer: 1. Entomophily Insect pollinated flowers (entomophily) need attractants such as colour and scent and rewards such as nectar and poll... 1
- Functional megaspore in an angiosperm develops into : Answer: 2. Embryo sac The functional megaspore divides mitotically to form the female gametophyte, the embryo sac. Endosperm and embryo form... 1
- The genotypes of a Husband and Wife are I^AI^B and I^Ai.Among the blood types of their children, how many different genotypes and phenotypes are possible ? Answer: 2. 4 genotypes ; 3 phenotypes Write the Punnett cross of the parents and count the distinct genotypes and blood groups. Gametes: I^A... 1
- Viroids differ from viruses in having : Answer: 3. RNA molecules without protein coat Viroids are smaller than viruses: they are infectious RNA molecules and have no protein coat.... 1
- Mycorrhizae are the example of : Answer: 3. Mutualism Mycorrhizae are associations between fungi and roots of higher plants, and both partners benefit. The fungus absorbs ph... 1