Practice Test - NEET MCQ

Explanation:

• Maxwell's equations describe how electric and magnetic fields interact with each other.


• One of Maxwell's equations states that a time-varying magnetic field acts as a source of electric field.


• This means that when a magnetic field changes over time, it induces an electric field in the surrounding space.


• Similarly, another Maxwell's equation states that a time-varying electric field acts as a source of magnetic field.


• Therefore, time-varying magnetic fields and time-varying electric fields are interconnected and can generate each other.


 

Option 2 : Microwaves

Concept:

• Frequencies range of Radio waves:  3KHz to 300GHz
• Frequencies range of Micro waves:  1GHz to 300GHz
• Frequencies range of Infrared waves:  300GHz to 400THz
• Frequencies range of light waves:  430THz to 750THz

The electromagnetic wave travels in vacuum along z-direction. Then, the electric field vector and magnetic field vector will be in the XY plane.
Frequency of the wave = 30 MHz
Converting into Hz, v = 30× 10⁶ Hz.
speed of light, c = 3 × 10⁸ m/s
Wavelength of the wave can be calculated using the following relation:
λ = c/v
⇒ λ = 3 × 10⁸/30 × 10⁶
⇒λ = 10 m

Light from each point on a luminous object travels outward in all directions in straight lines. Light travels at very high speeds, but is not instantaneously everywhere. Light from a point object travels indefinitely until it collides with matter in its path to be partially absorbed and reflected.

We know that,
Phase difference=K× path difference. K=2π/ λ.
Therefore, phase difference=(2π/ λ) ×( λ/3)=2π/3=120 degree.

Brewster's angle is an angle of incidence at which light with a particular polarization is perfectly transmitted through a transparent dielectric surface, with no reflection. When unpolarized light is incident at this angle, the light that is reflected from the surface is therefore perfectly polarized.

For zeroth order reaction

When reaction is 50% completed. 

x(product) formed after 15 s
= 0.025 Ms^-1 x 15s
= 0.375 M
Then, reactant left
= 0.500 - 0.375
= 0.125 M

For first order reaction,

time = 15 min to change its concentration from 0.8 m to 0.4 m Thus, 50% reaction.
Thus,  t₅₀ = 15 min

For first order reaction,

For the first order kinetic, 

Ans: 2
Sol: An alpha helix is a secondary structure of a protein because it involves the local coiling of the polypeptide chain into a helix, stabilized by hydrogen bonds between the backbone atoms. It is one of the common structural patterns found within proteins, distinct from the primary, tertiary, and quaternary structures.
4o

A deoxyriboncleotide of DNA is formed by cross-linking of three chemicals- deoxyribose sugar (C₅H₁₀O₄), a nitrogen base and phosphoric acid (H₃PO₄). The backbone of a DNA strand is built up of alternate deoxyribose and phosphoric acid grounds. The phosphate group is connected to carbon 5' of the sugar residue of its own nucleotide and cerbon 3' of the sugar residue of the next nucleotide by phosphodiester bonds.

Chitin is the second most abundant polysaccharide (after cellulose). Chitin is not a storage polysaccharide rather it is a structural homopolysaccharide which forms the structure component of fungal walls and exoskeleton of artropods. It is an unbranched polysaccharide formed of N- acetylglucosamine (NAG) monomers joined together by β−1,4 linkages.

Proteins are said to have quaternary structure if they consist of 2 or more polypeptide chains untied by force other than covalent bonds (i.e., not peptide are hydrogen bonds). The force that stabilise these aggregates are hydrogen bonds and electrostatic bonds formed between amino acids on the polypeptide chains. Haemoglobin, the oxygen-transporting protein of blood, is an example of quaternary structure. This protein consists of four peptide chains of two types-α and β chains that occur in pairs.

A. Cotton fibre is cellulose. The tainted form of cellulose is cotton and contains about 90% cellulose.

B. Exoskeleton of cockroach is Chitin. Chitin is the main component of the outer skeleton of the cockroaches and it is a fibrous material which consists of polysaccharides.  

C. Liver is glycogen which remains inside the body of animals in the form of stored energy.

D. Peeled potato is starch which is basically a sequence of units of glucose which is connected by glycosidic bonds.

E. Roots of Dahlia produces inulin, which can help the body deal with its own insulin needs. The Inulin molecules obtained from Dahlia tubers are called Dahlin. 

Correct option is B)

B-DNA is the most commonly found form of DNA in nature. This form of DNA is very narrow and elongated.
B-DNA contains 10 base pairs per turn and each turn is about 34 Å long.

Given figure represents a part of DNA molecules, in which phosphoric acid groups and deoxyribose sugars are linked together by means of phosphodiester bonds. The two DNA chains are antiparallel, i.e., they run parallel but in opposite directions. In one chain the direction is 5'→3' while in the opposite one it is 3'→5'. The chains are held together by hydrogen bonds between their bases. Adenine (A), a purine of one chain lies exactly opposite to thymine (T), a pyrimidine of the other chain . Similarly, cytosine (C), a primidine lies opposite to guanine (G) a purine. Three hydrogen bonds occur between cytosine and guanine (C≡G) at positions 1'−1',2'−6' and 6'−2'. There are two such hydrogen bonds between adenone and thymine (A=T) which are formed at positions 1'−3' and 6'−4'. Hydrogen bonds occur between hydrogen of one base and oxygen or nitrogen of the other base.

Mitosis is the type of cell division that ensures equal distribution of genetic material in daughter cells. Mitosis can occur both in diploid and haploid cells.
The main function of mitosis is to make copies of cells for growth and regeneration.

In plants, cytokinesis or division of cytoplasm occurs due to the formation of the cell plate.

In animals, cytokinesis occurs due to the formation of constriction in the middle cell membrane.

Cell growth results in disturbing the ratio between the nucleus and the cytoplasm.
Therefore, it becomes essential for the cell to divide to restore the nucleo-cytoplasmic ratio.

Chromosomes appeared beaded during the leptotene stage of the prophase of meiosis I, also the longest stage of meiosis cell division.
Chromatin materials start condensing after that stage.

The transition period between the M-phase of Meiosis I and M-phase II during which no replication of DNA occurs is called interkinesis.

Bivalent or tetrad formation takes place during the zygotene stage of prophase I, after synapsis has occurred and homologous chromosomes form pairs. However, the bivalent is distinct only in the next stage, pachytene.

In some lower plants and in some social insects haploid cells also divide by mitosis.

Pachytene: During the third substage of meiosis, the chromosomes continue to condense. Crossing over takes place at this stage and at each point of crossing over a chiasma is formed (singular: chiasma) between non-sister chromatids of homologous chromosomes.

Fig: Stages of Prophase I of Meiosis

The number of chromosomes and amount of DNA are changed in anaphase and S phase respectively.(i) In S phase, number of chromosomes remain same but each chromosome replicates so that it comes to have two chromatids. Due to this the DNA contents doubles from 1C to 2C or 2C to 4C depending upon haploid/diploid nature of cell.(ii) In Anaphase. In mitotic anaphase, number of chromosome remains the same. It is only sister chromatids which move towards their respective poles. DNA contents remain unchanged. In Anaphase-I of meiosis, number of chromosomes are reduced to half, i.e., from 2N to 1N. DNA contents decrease to one half in Anaphase-I of Meiosis-I from 2C to 1C