RRB ALP CBT 1 2025 PYQs

Concept: Refractive index of a medium n = c (speed in air/vacuum) ÷ v (speed in the medium).

1. $n=\frac{c}{v}=1.33$ ⇒ $c=1.33v$.
2. So light in air is 1.33 times faster than in water; light slows down in water.

Short trick: Memory hook: 'n = c by v' — bigger n, slower light (denser medium).

Answer: (B) The speed of light in air is 1.33 times the speed of light in water.

Concept: A compound always contains its elements in a fixed ratio by mass (C : O = 12 : 32 = 3 : 8 in CO₂).

1. 36 g C = 3 × 12 g.
2. Oxygen = 3 × 32 = 96 g.

Short trick: Carbon tripled → oxygen tripled. (Law given by Proust.)

Answer: (A) 96 g

Concept: Dried neem leaves act as a natural insect repellent in stored grain.

1. Neem contains azadirachtin, which repels and disrupts the growth of storage pests (weevils, beetles, moths).
2. It is a cheap, chemical-free method used at home and on farms.

Short trick: Hook: Neem = natural pesticide (azadirachtin).

Answer: (D) Insect infestation

Concept: Gastric glands in the stomach wall secrete HCl, pepsin and mucus.

1. HCl makes the medium acidic and kills germs; it activates pepsin for protein digestion.
2. Mucus protects the stomach lining from the acid.

Short trick: 'Gastric' = stomach (Greek gaster).

Answer: (B) Stomach

Concept: Unicellular organisms: a single cell performs all life functions.

1. Amoeba, Paramoecium (protozoa) and Chlamydomonas (green alga) are unicellular.
2. Cycas is a multicellular gymnosperm plant (a 'living fossil').

Short trick: Hook: Cycas = a tree-like plant you can see — never one cell.

Answer: (D) Cycas

Concept: The region around a magnet in which its force can be detected is its magnetic field.

1. It is a vector quantity (magnitude + direction); SI unit tesla (T).
2. Field lines go from N to S outside the magnet; they are closest near the poles (strongest field).

Short trick: 'Field' = region of influence (like gravitational field, electric field).

Answer: (B) Magnetic field

Concept: All distances are measured from the pole/optical centre; distances in the direction of incident light are +, opposite are −.

1. The object is placed to the left, and light travels left → right.
2. So the object distance (u) of a real object is measured against the incident light → negative.

Short trick: Hook: 'u is always negative' for a real object in front of a mirror or lens.

Answer: (C) Negative when the object is real

Concept: Valency = combining capacity = electrons lost, gained or shared to complete the octet.

1. If valence electrons are 1–3, valency = number of valence electrons.
2. If the shell is nearly full (5–7), valency = 8 − valence electrons, e.g. Cl (7) → 1, O (6) → 2.

Short trick: Hook: 'Few → give, Many → take' — nearly full shells take electrons (8 − n).

Answer: (D) By the number of electrons needed to complete the octet

Concept: Electrolysis of brine (aq. NaCl): $2NaCl+2H_{2}O\to 2NaOH+C{l}_2+H_2$.

1. Anode (+) attracts Cl⁻ ions → oxidised to Cl₂ gas.
2. Cathode (−) reduces water → H₂ gas; OH⁻ left there combines with Na⁺ → NaOH forms near the cathode.
3. So H₂ at cathode, Cl₂ at anode.

Short trick: Name = products: Chlor (Cl₂, at anode) + Alkali (NaOH, at cathode) with H₂ at cathode. Mnemonic: “Cl₂ at Anode, H₂ at Cathode”.

Answer: (A) Hydrogen gas is released at the cathode and chlorine gas at the anode.

Concept: Wave speed $v=f\lambda$; time $t=\frac{d}{v}$.

1. $v=4000\times 0.25=1000$ m/s.
2. $t=\frac{2500}{1000}=2.5$ s.

Short trick: Convert first: 4 kHz × 25 cm = 4000 × ¼ m = 1 km/s → 2.5 km takes 2.5 s.

Answer: (D) 2.5 s

Concept: Xylem carries water and minerals from roots upward; phloem carries food.

1. Xylem vessels and tracheids form continuous tubes from roots to leaves.
2. Transpiration pull draws water up through them.
3. Phloem translocates sugars; sclerenchyma/parenchyma are support/storage tissues.

Short trick: Memory hook: Xylem = eXport of water up; Phloem = Food.

Answer: (A) Xylem

Concept: $KE=\frac{1}{2}m{v}^2$.

1. $72=\frac{1}{2}\times 4\times v^2=2v^2$.
2. $v^2=36$ → $v=6$ m/s.

Short trick: $v=\sqrt{\frac{2KE}{m}}=\sqrt{\frac{144}{4}}=6$.

Answer: (D) 6 m/s

Concept: A double concave lens is thicker at the edges and thinner at the middle; it is a diverging lens.

1. Parallel rays spread out after passing through it.
2. The refracted rays appear to come from the principal focus F on the same side.
3. A convex lens (thick middle) converges; option C describes a plain glass slab.

Short trick: Concave = caved in at the middle → thin centre → spreads (diverges) light.

Answer: (D) It is thicker at the edges and thinner in the middle; it diverges light rays.

Concept: Mechanical control = physically removing or destroying weeds.

1. Hand weeding, hoeing, tilling and harrowing are mechanical methods.
2. Spraying herbicides (weedicides) is chemical control.
3. Crop rotation is a cultural/preventive method; seed treatment protects seeds from pests/diseases.

Short trick: Mechanical = by hand or machine; Chemical = by spray.

Answer: (B) Hand weeding

Concept: Excretion removes harmful metabolic wastes (CO₂, urea, etc.) produced in the body.

1. Respiration and other energy-releasing reactions make CO₂, water and nitrogenous wastes.
2. Their removal (by kidneys, lungs, skin) is excretion.
3. Nutrition takes in food, circulation transports, digestion breaks food down.

Short trick: Excretion = Exit of metabolic waste (undigested food leaving = egestion, not excretion).

Answer: (A) Excretion

Concept: A proton carries a unit positive charge (+1.6 × 10⁻¹⁹ C) and has mass ≈ 1.67 × 10⁻²⁷ kg.

1. Electron mass ≈ 9.1 × 10⁻³¹ kg → proton ≈ 1836 ≈ 2000 times heavier.
2. Neutron: no charge (option B); electron: negative and outside the nucleus (C wrong).
3. Option D wrongly equates the masses.

Short trick: Proton = Positive + Plump (≈ 1836 × electron).

Answer: (A) It is positively charged and has a mass approximately 2000 times that of an electron.

Concept: Weight $W=mg$; mass stays the same everywhere, but $g$ depends on the mass and radius of the planet.

1. $g_{moon}\approx \frac{1}{6}{g}_{earth}$ because the Moon’s mass is much smaller.
2. So the same object weighs about one-sixth on the Moon.
3. It is not zero – the Moon still attracts the object.

Short trick: Memory hook: “Moon = 1/6” – a 60 kg-weight person feels like 10 kg there.

Answer: (C) Less on the Moon

Concept: Ventricles are pumping chambers; atria are receiving chambers.

1. The ventricles must push blood to the lungs (right) and the whole body (left).
2. This needs high pressure, so their walls are thick and muscular (left ventricle thickest).
3. Atria only receive blood and pass it a short distance, so their walls are thin.

Short trick: Hook: “Ventricle = Venture out” – blood leaves the heart from ventricles, so they need strong muscles.

Answer: (B) To pump blood with high pressure

Concept: In stained onion peel / cheek cells, the nucleus is darkly stained; the rest inside the membrane is lightly stained.

1. The fluid content inside the plasma membrane (excluding nucleus) is the cytoplasm.
2. Iodine / methylene blue stain the nucleus darker than the cytoplasm.
3. Cheek cells have no cell wall; vacuoles are not the lightly stained “region”.

Short trick: Hook: “Dark dot = Nucleus, light background = Cytoplasm.”

Answer: (C) Cytoplasm

Concept: Each nephron begins with a cup-shaped Bowman’s capsule enclosing the glomerulus.

1. The glomerulus is the bunch of capillaries inside the cup.
2. Bowman’s capsule is the cup itself at the start of the coiled tubule – filtration happens here.
3. Loop of Henle and collecting duct are further along the tube.

Short trick: Hook: “Bowman’s Bowl” – capsule = cup; glomerulus = the ball in the cup.

Answer: (C) Bowman’s capsule