What would be expected to happen if:
Question: What would be expected to happen if: (a) $\mathrm{GA}_{3}$ is applied to rice seedlings (b) Dividing cells stop differentiating (c) A rotten fruit gets mixed with unripe fruits (d) You forget to add cytokinin to the culture medium. Solution: (a) If $\mathrm{GA}_{3}$ is applied to rice seedlings, then the rice seedlings will exhibit internode-elongation and increase in height. (b)If dividing cells stop differentiating, then the plant organs such as leaves and stem will not be formed. Th...
Read More →A rocket is fired from the earth towards the sun.
Question: A rocket is fired from the earth towards the sun. At what distance from the earth's centre is the gravitational force on the rocket zero? Mass of the sun $=2 \times 10^{30} \mathrm{~kg}$, mass of the earth $=6 \times 10^{24} \mathrm{~kg}$. Neglect the effect of other planets etc. (orbital radius $=1.5 \times 10^{11} \mathrm{~m}$ ). Solution: Mass of the Sun, $M_{s}=2 \times 10^{30} \mathrm{~kg}$ Mass of the Earth, $M_{\mathrm{e}}=6 \times 10^{24} \mathrm{~kg}$ Orbital radius, $r=1.5 \t...
Read More →What is the significance of meiosis?
[question] Question. What is the significance of meiosis? [/question] [solution] Solution: Meiosis is the process involving the reduction in the amount of genetic material. It comprises two successive nuclear and cell divisions, with a single cycle of DNA replication. As a result, at the end of meiosis II, four haploid cells are formed. Significance of meiosis 1. Meiosis maintains the chromosome number from generation to generation. It reduces the chromosome number to half so that the process of...
Read More →Would a defoliated plant respond to photoperiodic cycle? Why?
Question: Would a defoliated plant respond to photoperiodic cycle? Why? Solution: A defoliated plant will not respond to the photoperiodic cycle. It is hypothesised that the hormonal substance responsible for flowering is formed in the leaves, subsequently migrating to the shoot apices and modifying them into flowering apices. Therefore, in the absence of leaves, light perception would not occur, i.e., the plant would not respond to light....
Read More →Which one of the plant growth regulators would you use if you are asked to:
Question: Which one of the plant growth regulators would you use if you are asked to: (a) Induce rooting in a twig (b) Quickly ripen a fruit (c) Delay leaf senescence (d) Induce growth in axillary buds (e) Bolt a rosette plant (f) Induce immediate stomatal closure in leaves. Solution: (a)Induce rooting in a twig Auxins (b)Quickly ripen a fruit Ethylene (c)Delay leaf senescence Cytokinins (d)Induce growth in axillary buds Cytokinins (e)Bolt a rosette plant Gibberellic acid (f)Induce immediate sto...
Read More →The work function for caesium atom is 1.9 eV. Calculate (a) the threshold wavelength and (b) the threshold frequency of the radiation
[question] Question. The work function for caesium atom is $1.9 \mathrm{eV}$. Calculate (a) the threshold wavelength and (b) the threshold frequency of the radiation. If the caesium element is irradiated with a wavelength $500 \mathrm{~nm}$, calculate the kinetic energy and the velocity of the ejected photoelectron. [/question] [solution] Solution: It is given that the work function $\left(W_{0}\right)$ for caesium atom is $1.9 \mathrm{eV}$. (a) From the $W_{0}=\frac{h c}{\lambda_{0}}$ expressio...
Read More →‘Both a short day plant and a long day plant can flower simultaneously in a given place’. Explain.
Question: Both a short day plant and a long day plant can flower simultaneously in a given place. Explain. Solution: The flowering response in short-day plants and long-day plants is dependent on the durations for which these plants are exposed to light. The short-day plant and long-day plant can flower at the same place, provided they have been given an adequate photoperiod....
Read More →‘Both a short day plant and a long day plant can flower simultaneously in a given place’. Explain.
Question: Both a short day plant and a long day plant can flower simultaneously in a given place. Explain. Solution: The flowering response in short-day plants and long-day plants is dependent on the durations for which these plants are exposed to light. The short-day plant and long-day plant can flower at the same place, provided they have been given an adequate photoperiod....
Read More →Choose the correct answer from among the given ones:
Question: Choose the correct answer from among the given ones: The gravitational intensity at the centre of a hemispherical shell of uniform mass density has the direction indicated by the arrow (see Fig 8.12) (i) a, (ii) b, (iii) c, (iv) O. Solution: Answer:(iii) Gravitational potential (V) is constant at all points in a spherical shell. Hence, the gravitational potential gradientis zero everywhere inside the spherical shell. The gravitational potential gradient is equal to the negative of grav...
Read More →‘Both growth and differentiation in higher plants are open’. Comment.
Question: Both growth and differentiation in higher plants areopen. Comment. Solution: Growth and development in higher plants is referred to as beingopen. This is because various meristems, having the capacity for continuously dividing and producing new cells, are present at different locations in these plant bodies....
Read More →Which of the following symptoms is likely to afflict an astronaut in space
Question: Which of the following symptoms is likely to afflict an astronaut in space (a) swollen feet, (b) swollen face, (c) headache, (d) orientational problem? Solution: Answer:(b), (c), and (d) (a)Legs hold the entire mass of a body in standing position due to gravitational pull. In space, an astronaut feels weightlessness because of the absence of gravity. Therefore, swollen feet of an astronaut do not affect him/her in space. (b)A swollen face is caused generally because of apparent weightl...
Read More →Why is Abscisic acid also known as stress hormone?
Question: Why is Abscisic acid also known as stress hormone? Solution: Abscisic acid is called stress hormones as it induces various responses in plants against stress conditions. It increases the tolerance of plants toward various stresses. It induces the closure of the stomata during water stress. It promotes seed dormancy and ensures seed germination during favourable conditions. It helps seeds withstand desiccation. It also helps in inducing dormancy in plants at the end of the growing seaso...
Read More →A comet orbits the Sun in a highly elliptical orbit.
Question: A comet orbits the Sun in a highly elliptical orbit. Does the comet have a constant (a) linear speed, (b) angular speed, (c) angular momentum, (d) kinetic energy, (e) potential energy, (f) total energy throughout its orbit? Neglect any mass loss of the comet when it comes very close to the Sun. Solution: a)No (b)No (c)Yes (d)No (e)No (f)Yes Angular momentum and total energy at all points of the orbit of a comet moving in a highly elliptical orbit around the Sun are constant. Its linear...
Read More →The size of isoelectronic species
Question: The size of isoelectronic species $-\mathrm{F}^{-}, \mathrm{Ne}$ and $\mathrm{Na}^{+}$is affected by (a) Nuclear charge (Z) (b) Valence principal quantum number (n) (c) Electron-electron interaction in the outer orbitals (d) None of the factors because their size is the same. Solution: The size of an isoelectronic species increases with a decrease in the nuclear charge (Z). For example, the order of the increasing nuclear charge of F, Ne, and Na+is as follows: $\mathrm{F}^{-}\mathrm{Ne...
Read More →What do you understand by photoperiodism and vernalisation?
Question: What do you understand by photoperiodism and vernalisation? Describe their significance. Solution: Photoperiodism refers to the response of plants with respect to the duration of light (i.e., period of day and night). On the basis of its response to the duration of light, a plant is classified as a short-day plant, a long-day plant, or a day-neutral plant. Short-day plants flower when they are exposed to light for a period less than the critical day-length (for example:Chrysanthemum). ...
Read More →Does the escape speed of a body from the earth depend on
Question: Does the escape speed of a body from the earth depend on (a)the mass of the body, (b)the location from where it is projected, (c)the direction of projection, (d)the height of the location from where the body is launched? Solution: (a)No (b)No (c)No (d)Yes Escape velocity of a body from the Earth is given by the relation: $v_{\mathrm{esc}}=\sqrt{2 \mathrm{~g} R}$(i) g = Acceleration due to gravity R= Radius of the Earth It is clear from equation (i) that escape velocity $v_{\text {esc }...
Read More →Choose the correct alternative:
Question: Choose the correct alternative: (a)If the zero of potential energy is at infinity, the total energy of an orbiting satellite is negative of its kinetic/potential energy. (b)The energy required to launch an orbiting satellite out of earths gravitational influence is more/less than the energy required to project a stationary object at the same height (as the satellite) out of earths influence. Solution: (a)Kinetic energy (b)Less (a) Total mechanical energy of a satellite is the sum of it...
Read More →Let us assume that our galaxy consists of 2.5 × 1011 stars each of one solar mass.
Question: Let us assume that our galaxy consists of $2.5 \times 10^{11}$ stars each of one solar mass. How long will a star at a distance of 50,000 ly from the galactic centre take to complete one revolution? Take the diameter of the Milky Way to be $10^{5}$ ly. Solution: Mass of our galaxy Milky Way, $M=2.5 \times 10^{11}$ solar mass Solar mass $=$ Mass of Sun $=2.0 \times 10^{36} \mathrm{~kg}$ Mass of our galaxy, $M=2.5 \times 10^{11} \times 2 \times 10^{36}=5 \times 10^{41} \mathrm{~kg}$ Diam...
Read More →Evaluate
[question] Question. Evaluate (i) $\frac{\sin ^{2} 63^{\circ}+\sin ^{2} 27^{\circ}}{\cos ^{2} 17^{\circ}+\cos ^{2} 73^{\circ}}$ (ii) $\sin 25^{\circ} \cos 65^{\circ}+\cos 25^{\circ} \sin 65^{\circ}$ [/question] [solution] Solution: (i) $\frac{\sin ^{2} 63^{\circ}+\sin ^{2} 27^{\circ}}{\cos ^{2} 17^{\circ}+\cos ^{2} 73^{\circ}}$ $=\frac{\left\{\sin \left(90^{\circ}-27^{\circ}\right)\right\}^{2}+\sin ^{2} 27^{\circ}}{\cos ^{2} 17^{\circ}+\left\{\cos \left(90^{\circ}-17^{\circ}\right)\right\}^{2}}$...
Read More →List the main differences between mitosis and meiosis.
[question] Question. List the main differences between mitosis and meiosis. [/question] [solution] Solution: [/solution]...
Read More →Anything that influences the valence electrons will affect the chemistry of the element.
Question: Anything that influences the valence electrons will affect the chemistry of the element. Which one of the following factors does not affect the valence shell? (a) Valence principal quantum number (n) (b) Nuclear charge (Z) (c) Nuclear mass (d) Number of core electrons. Solution: Nuclear mass does not affect the valence electrons...
Read More →Write all the other trigonometric ratios of $\angle \mathrm{A}$ in terms of $\sec \mathrm{A}$.
[question] Question. Write all the other trigonometric ratios of $\angle \mathrm{A}$ in terms of $\sec \mathrm{A}$. [/question] [solution] Solution: (i) $\sin A=\sqrt{1-\cos ^{2} A}$ $=\sqrt{1-\frac{1}{\sec ^{2} A}}=\frac{\sqrt{\sec ^{2} A-1}}{\sec A}$ (ii) $\cos A=\frac{1}{\sec A}$ (iii) $\tan A=\sqrt{\sec ^{2} \mathbf{A}-\mathbf{1}}$ (iv) $\cot A=\frac{1}{\tan A}=\frac{1}{\sqrt{\sec ^{2} A-1}}$ (v) $\operatorname{cosec} A=\frac{1}{\sin A}=\frac{\sec A}{\sqrt{\sec ^{2} A-1}}$ [/solution]...
Read More →Io, one of the satellites of Jupiter, has an orbital period of 1.769 days and the radius of the orbit is 4.22 × 108 m.
Question: Io, one of the satellites of Jupiter, has an orbital period of $1.769$ days and the radius of the orbit is $4.22 \times 10^{8} \mathrm{~m}$. Show that the mass of Jupiter is about one-thousandth that of the sun. Solution: Orbital period of $I_{0}, T_{l o}=1.769$ days $=1.769 \times 24 \times 60 \times 60 \mathrm{~s}$ Orbital radius of $I_{0}, R_{b}=4.22 \times 10^{8} \mathrm{~m}$ Satellite $I_{0}$ is revolving around the Jupiter Mass of the latter is given by the relation: $M_{J}=\frac...
Read More →Distinguish anaphase of mitosis from anaphase I of meiosis.
[question] Question. Distinguish anaphase of mitosis from anaphase I of meiosis. [/question] [solution] Solution: \ [/solution]...
Read More →Express the following rational numbers as decimals:
Question: Express the following rational numbers as decimals:(i) $\frac{42}{100}$(ii) $\frac{327}{500}$(iii) $\frac{15}{4}$ Solution: (i) Given rational number is $\frac{42}{100}$ Now we have to express this rational number into decimal form. So we will use long division method as below. Hence, $\frac{42}{100}=0.42$ (ii) Given rational number is $\frac{327}{500}$ Now we have to express this rational number into decimal form. So we will use long division method as below. Hence, $\frac{327}{500}=0...
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