List five main groups of natural plant growth regulators.
Question: List five main groups of natural plant growth regulators. Write a note on discovery, physiological functions and agricultural/horticultural applications of any one of them. Solution: Plant growth regulators are the chemical molecules secreted by plants affecting the physiological attributes of a plant. There are five main plant growth regulators. These are: (i) Auxins (ii) Gibberellic acid (iii) Cytokinins (iv) Ethylene (v) Abscisic acid (i) Auxins Discovery: The first observations reg...
Read More →Express the trigonometric ratios sin A,
[question] Question. Express the trigonometric ratios sin A, sec A and tan A in terms of cot A. [/question] [solution] Solution: We have $\operatorname{cosec}^{2} A-\cot ^{2} A=1$ $\Rightarrow \operatorname{cosec}^{2} A=1+\cot ^{2} A$ $\Rightarrow(\operatorname{cosec} A)^{2}=\cot ^{2} A+1$ $\Rightarrow\left(\frac{1}{\sin A}\right)^{2}=\cot ^{2} A+1$ $\Rightarrow(\sin \mathrm{A})^{2}=\frac{\mathbf{1}}{\cot ^{2} \mathbf{A}+\mathbf{1}}$ $\Rightarrow \sin A=\pm \frac{1}{\sqrt{\cot ^{2} A+1}}$ We rej...
Read More →Describe briefly:
Question: Describe briefly: (a) Arithmetic growth (b) Geometric growth (c) Sigmoid growth curve (d) Absolute and relative growth rates Solution: (a) Arithmetic growth In arithmetic growth, one of the daughter cells continues to divide, while the other differentiates into maturity. The elongation of roots at a constant rate is an example of arithmetic growth. (b) Geometric growth Geometric growth is characterised by a slow growth in the initial stages and a rapid growth during the later stages. T...
Read More →Find examples where the four daughter cells
[question] Question. Find examples where the four daughter cells from meiosis are equal in size and where they are found unequal in size. [/question] [solution] Solution: (a) Spermatogenesis or the formation of sperms in human beings occurs by the process of meiosis. It results in the formation of four equal-sized daughter cells. (b) Oogenesis or the formation of ovum in human beings occurs by the process of meiosis. It results in the formation of four daughter cells which are unequal in size. [...
Read More →Which of the following statements related to the modern periodic table is incorrect?
Question: Which of the following statements related to the modern periodic table is incorrect? (a) Thep-block has 6 columns, because a maximum of 6 electrons can occupy all the orbitals in ap-shell. (b) Thed-block has 8 columns, because a maximum of 8 electrons can occupy all the orbitals in ad-subshell. (c) Each block contains a number of columns equal to the number of electrons that can occupy that subshell. (d) The block indicates value of azimuthal quantum number (l) for the last subshell th...
Read More →Suppose there existed a planet that went around the sun twice as fast as the earth.
Question: Suppose there existed a planet that went around the sun twice as fast as the earth.What would be its orbital size as compared to that of the earth? Solution: Lesser by a factor of 0.63 Time taken by the Earth to complete one revolution around the Sun, $T_{e}=1$ year Orbital radius of the Earth in its orbit, $R_{e}=1 \mathrm{AU}$ Time taken by the planet to complete one revolution around the Sun, $T_{p}=\frac{1}{2} T_{e}=\frac{1}{2}$ year Orbital radius of the planet $=R_{p}$ From Keple...
Read More →In the modern periodic table, the period indicates the value of:
Question: In the modern periodic table, the period indicates the value of: (a) Atomic number (b) Atomic mass (c) Principal quantum number (d) Azimuthal quantum number. Solution: The value of the principal quantum number (n) for the outermost shell or the valence shell indicates a period in the Modern periodic table....
Read More →In the modern periodic table, the period indicates the value of:
Question: In the modern periodic table, the period indicates the value of: (a) Atomic number (b) Atomic mass (c) Principal quantum number (d) Azimuthal quantum number. Solution: The value of the principal quantum number (n) for the outermost shell or the valence shell indicates a period in the Modern periodic table....
Read More →How does cytokinesis in plant cells differ from that in animal cells?
[question] Question. How does cytokinesis in plant cells differ from that in animal cells? [/question] [solution] Solution: [/solution]...
Read More →Why is not any one parameter good enough to demonstrate growth throughout the life of a flowering plant?
Question: Why is not any one parameter good enough to demonstrate growth throughout the life of a flowering plant? Solution: In plants, growth is said to have taken place when the amount of protoplasm increases. Measuring the growth of protoplasm involves many parameters such as the weight of the fresh tissue sample, the weight of the dry tissue sample, the differences in length, area, volume, and cell number measured during the growth period. Measuring the growth of plants using only one parame...
Read More →Predict the formula of the stable binary compounds that would be formed by the combination of the following pairs of elements.
Question: Predict the formula of the stable binary compounds that would be formed by the combination of the following pairs of elements. (a) Lithium and oxygen (b) Magnesium and nitrogen (c) Aluminium and iodine (d) Silicon and oxygen (e) Phosphorus and fluorine (f) Element 71 and fluorine Solution: (a) $\mathrm{Li}_{2} \mathrm{O}$ (b) $\mathrm{Mg}_{3} \mathrm{~N}_{2}$ (c) $\mathrm{All}_{3}$ (d) $\mathrm{SiO}_{2}$ (e) $\mathrm{PF}_{3}$ or $\mathrm{PF}_{5}$ (f) The element with the atomic number ...
Read More →Define growth, differentiation, development, dedifferentiation, redifferentiation, determinate growth, meristem and growth rate.
Question: Define growth, differentiation, development, dedifferentiation, redifferentiation, determinate growth, meristem and growth rate. Solution: (a) Growth It is an irreversible and permanent process, accomplished by an increase in the size of an organ or organ parts or even of an individual cell. (b) Differentiation It is a process in which the cells derived from the apical meristem (root and shoot apex) and the cambium undergo structural changes in the cell wall and the protoplasm, becomin...
Read More →Choose the correct alternative:
Question: Choose the correct alternative: (a)Acceleration due to gravity increases/decreases with increasing altitude. (b)Acceleration due to gravity increases/decreases with increasing depth. (assume the earth to be a sphere of uniform density). (c)Acceleration due to gravity is independent of mass of the earth/mass of the body. (d) The formula $-G M m\left(1 / r_{2}-1 / r_{1}\right)$ is more/less accurate than the formula $m g\left(r_{2}-r_{1}\right)$ for the difference of potential energy bet...
Read More →Express $\sin 67^{\circ}+\cos 75^{\circ}$
[question] Question. Express $\sin 67^{\circ}+\cos 75^{\circ}$ in terms of trigonometric ratios of angles between $0^{\circ}$ and $45^{\circ}$. [/question] [solution] Solution: sin 67° + cos 75° = sin(90° – 23°) + cos (90° – 15°) = cos 23° + sin 15° [/solution]...
Read More →Lifetimes of the molecules in the excited states are often measured
[question] Question. Lifetimes of the molecules in the excited states are often measured by using pulsed radiation source of duration nearly in the nano second range. If the radiation source has the duration of $2 \mathrm{~ns}$ and the number of photons emitted during the pulse source is $2.5 \times$ $10^{15}$, calculate the energy of the source. [/question] [solution] Solution: Frequency of radiation (v), $v=\frac{1}{2.0 \times 10^{-9} \mathrm{~s}}$ $v=5.0 \times 10^{8} \mathrm{~s}^{-1}$ Energy...
Read More →The first (ΔiH1) and the second (ΔiH) ionization enthalpies (in kJ mol–1) and the (ΔegH) electron gain enthalpy
Question: The first $(\Delta ; H 1)$ and the second $(\Delta, H)$ ionization enthalpies $\left(\right.$ in $\left.\mathrm{kJ} \mathrm{mol}^{-1}\right)$ and the $\left(\Delta_{\mathrm{eg}} H\right)$ electron gain enthalpy $\left(\right.$ in $\left.\mathrm{kJ} \mathrm{mol}^{-1}\right)$ of a few elements are given below: Which of the above elements is likely to be : (a) the least reactive element. (b) the most reactive metal. (c) the most reactive non-metal. (d) the least reactive non-metal. (e) th...
Read More →Answer the following:
Question: Answer the following: (a)You can shield a charge from electrical forces by putting it inside a hollow conductor. Can you shield a body from the gravitational influence of nearby matter by putting it inside a hollow sphere or by some other means? (b)An astronaut inside a small space ship orbiting around the earth cannot detect gravity. If the space station orbiting around the earth has a large size, can he hope to detect gravity? (c)If you compare the gravitational force on the earth du...
Read More →What is the significance of step-wise release of energy in respiration?
Question: What is the significance of step-wise release of energy in respiration? Solution: The process of aerobic respiration is divided into four phases glycolysis, TCA cycle, ETS, and oxidative phosphorylation. It is generally assumed that the process of respiration and production of ATP in each phase takes place in a step-wise manner. The product of one pathway forms the substrate of the other pathway. Various molecules produced during respiration are involved in other biochemical processes....
Read More →If A, B and C are interior angles of a triangle ABC,
[question] Question. If $A, B$ and $C$ are interior angles of a triangle $A B C$, then show that $\sin \left(\frac{B+C}{2}\right)=\cos \frac{A}{2} .$ [/question] [solution] Solution: A + B + C = 180° $\Rightarrow \mathrm{B}+\mathrm{C}=180^{\circ}-\mathrm{A}$ $\Rightarrow \frac{\mathbf{B}+\mathbf{C}}{2}=\frac{180^{\circ}-\mathbf{A}}{2} \Rightarrow \frac{\mathbf{B}+\mathbf{C}}{2}=\left(\mathbf{M}^{\circ}-\frac{\mathbf{A}}{2}\right)$ $\Rightarrow \sin \left(\frac{\mathbf{B}+\mathbf{C}}{\mathbf{2}}\...
Read More →Describe the following:
[question] Question. Describe the following: (a) synapsis (b) bivalent (c) chiasmata Draw a diagram to illustrate your answer. [/question] [solution] Solution: (a) Synapsis The pairing of homologous chromosomes is called synapsis. This occurs during the second stage of prophase I or zygotene. (b) Bivalent Bivalent or tetrad is a pair of synapsed homologous chromosomes. They are formed during the zygotene stage of prophase I of meiosis. (c) Chiasmata Chiasmata is the site where two non-sister chr...
Read More →If sec 4 A = cosec (A – 20°),
[question] Question. If sec 4 A = cosec (A – 20°), where 4 A is an acute angle, find the value of A. [/question] [solution] Solution: sec 4 A = cosec (A – 20°) $\Rightarrow \operatorname{cosec}\left(90^{\circ}-4 \mathrm{~A}\right)=\operatorname{cosec}\left(\mathrm{A}-20^{\circ}\right)$ $\left\{\because \operatorname{cosec}\left(90^{\circ}-\theta\right)=\sec \theta\right\}$ $\Rightarrow 90^{\circ}-4 \mathrm{~A}=\mathrm{A}-20^{\circ}$ $\Rightarrow 5 \mathrm{~A}=110^{\circ} \Rightarrow \mathrm{A}=2...
Read More →Show that $\mathbf{a} .(\mathbf{b} \times \mathbf{c})$ is equal in magnitude to the volume
[question] Question. Show that $\mathbf{a} .(\mathbf{b} \times \mathbf{c})$ is equal in magnitude to the volume of the parallelepiped formed on the three vectors, $\mathbf{a}, \mathbf{b}$ and $\mathbf{c}$. [/question] [solution] solution: A parallelepiped with origin O and sides a, b, and c is shown in the following figure. Volume of the given parallelepiped = abc $\overrightarrow{\mathrm{OC}}=\vec{a}$ $\overrightarrow{\mathrm{OB}}=\vec{b}$ $\overrightarrow{\mathrm{OC}}=\vec{c}$ Let $\hat{\mathb...
Read More →What is oxidative phosphorylation?
Question: What is oxidative phosphorylation? Solution: Oxidative phosphorylation is a process in which electrons are transferred from electron donors to oxygen, which acts as electron acceptor. The oxidation-reduction reactions are involved in the formation of proton gradient. The main role in oxidative phosphorylation is played by the enzyme ATP synthase (complex V). This enzyme complex consists of $F_{0}$ and $F_{1}$ components. The $F_{1}$ headpiece is a peripheral membrane protein complex an...
Read More →Assign the position of the element having outer electronic configuration
Question: Assign the position of the element having outer electronic configuration (i) $n s^{2} n p^{4}$ for $n=3$ (ii) $(n-1) d^{2} n s^{2}$ for $n=4$, and (iii) $(n-2) f^{7}(n-1) d^{1} n s^{2}$ for $n=6$, in the periodic table. Solution: (i)Sincen= 3, the element belongs to the 3rdperiod. It is apblock element since the last electron occupies theporbital. There are four electrons in theporbital. Thus, the corresponding group of the element = Number ofsblock groups + number ofdblock groups + nu...
Read More →If tan A = cot B, prove that A + B = 90°.
[question] Question. If tan A = cot B, prove that A + B = 90°. [/question] [solution] Solution: tan A = cot B tan A = tan (90°–B) $\therefore \mathrm{A}=90^{\circ}-\mathrm{B}$ A + B = 90° [/solution]...
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