Explanation

When two circles touch each other externally, they have a single point of contact.

The distance between their centers (C1C2) is equal to the sum of their radii (r1 + r2).

Explanation

When an object is placed at the principal focus (F) of a convex lens, the rays emerge parallel after refraction.

Parallel rays appear to meet at infinity, so the image is formed at infinity (very far away).

Explanation

Lizards and snakes belong to the order Squamata, which is characterized by scaled reptiles.

This order includes both suborders: Lacertilia (lizards) and Serpentes (snakes).

Explanation

o-Nitrophenol is more acidic due to the strong electron-withdrawing effect of the nitro group and possible intramolecular hydrogen bonding, which stabilizes the conjugate base.

Though both have -NO₂, the ortho position enhances acidity more than the para position.

Explanation

Sabin vaccine is the oral polio vaccine (OPV) developed by Albert Sabin.

It contains live attenuated poliovirus.

It helps in building immunity against poliomyelitis.

Explanation

Dinoflagellates do have cellulose plates, but not impregnated with calcium — that’s a feature of some other protists, not typical dinoflagellates.

They are mostly unicellular and can form blooms (like red tides).

Explanation

1,2-Butadiene contains cumulene structure with adjacent double bonds (C=C=C), leading to sp-hybridization at the central carbon.

The terminal carbon atoms are sp²-hybridized, while the central carbon is sp-hybridized.

Explanation

Hormones are chemical messengers that travel through the bloodstream to target organs and tissues.

This is a key function of the circulatory system, helping regulate various bodily functions.

Explanation

Restoring force 𝐹 = −𝑘𝑥 depends on displacement 𝑥.

At the mid position, x = 0, so restoring force is minimum (zero).

Explanation

The energy density (u) in a capacitor is given by:

u = ½ε₀E²

Where:

- ε₀ is the permittivity of free space

- E is the electric field intensity between the plates

This shows that the energy density is proportional to the square of the electric field intensity (E²).