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P.E = -p . E = -pE cos\(\theta\)

\(\therefore\) P.E. is the maximum when cos\(\theta\) = -1, i.e

\(\theta\) = \(\pi\)(180°)

Correct answer is (c) Dead and decaying matter

1. Animals which are well-adapted to live in deserts are called xerocoles. These animals show adaptations for water conservation or heat tolerance. 

2. These animals show low basal metabolic rate. They obtain moisture from succulent plants and rarely drink water. E.g Gazella and Oryx. 

3. Desert animals like camel produce concentrated urine and dry dung. 

4. Many other hot desert animals are nocturnal, seeking out shade during the day or dwelling underground in burrows. 

5. Smaller animals from desert, emerge from their burrows at night. 

6. Mammals living in cold deserts have developed greater insulation through warmer body fur and insulating layers of fat beneath the skin. 

7. Few adaptations to desert life are unable to cool themselves by sweating so they shelter during the heat of the day. Many desert reptiles are ambush predators and often bury themselves in the sand, waiting for prey to come within range. 

8. Other animals have bodies designed to save water. Scorpions and wolf spiders have a thick outer covering which reduces moisture loss. The kidneys of desert animals concentrate urine, so that they excrete less water.

Correct option is  A) H, C

C) nano tubes

Correct answer is (a) Living together

C) Pull the hands back

People who cannot see nearby object very clearly but can see far objects clearly and is said to have a defect called hypermetropia. This defect is corrected by wearing spectacles made of convex lenses.

1. Iris 

2. concave

3. towards

1. (T) 

2. (F) 

3. (F) 

4. (T) 

5. (T) 

6. (T) 

7. (T) 

8. (F) 

9. (F) 

10. (T)

In cataract, the lens of the eye becomes small

1. (d)

2. (a)

3. (b) 

4. (a)

(i) ↔ (d) 

(ii) ↔ (e) 

(iii) ↔ (c) 

(iv) ↔ (b) 

(v) ↔ (a)

When a light ray enters from one medium to another medium, then it deviates from its path. This phenomenon is called refraction of light.

Cause of Refraction: The speed of light in denser medium (glass) is less than rarer medium (air). Hence it is clear that when light enters in the denser medium from rarer medium its speed becomes slow, on the other hand when it enters from denser to the rarer medium, it’s speed increases.

Hence phenomenon of refraction takes place due to difference in speed of travelling from one medium to another.

Raghav is suffering from far sightedness or hypermetropia. It is corrected by using convex lens. Megha is suffering from shortsightedness or myopia. It is corrected by using concave lens.

The image which cannot be obtained on screen is called Virtual.

(b) Dispersion

(a) Obliquely; making a large angle of incidence.

(b) Perpendicular to the glass surface

Yes, when angle of incidence is equal to critical angle then angle of refraction is equal to 90°.

During refraction of light velocity of light changes and also wavelength and amplitude. Frequency does not change during refraction.

Correct option is  A) increases

Lateral shift: 

The distance between incident and emergent ray is called lateral shift. 

Vertical shift : 

The perpendicular distance between object and its image is called vertical shift.

The property of liquid due to which its free surface tries to have minimum surface area is called surface tension.

∴ A small liquid drop has spherical shape due to surface tension.

C) both A and B

This happens due to elastic fatigue in spring.

 C)  \(\frac{Thickness \,of \,the \,glass \,slab}{Thickness \,of\, the \,glass \,slab\, – \,verticalshift}\)

When a spring balance has been used for a long time, it develops an elastic fatigue, the spring of such a balance takes longer time to recover its original configuration and therefore, it does not give correct measurement

Correct option is  A) 2 times

A) Xenon, Cesium

Correct option is D) Nuclear

Correct option is D) Cobalt

Correct option is C) Cobalt

(a) is more accurate because it is correct upto four places of decimal i.e. it has greater no of significant figures.

A volumetric flask is used to prepare a known volume of a solution in laboratory.

• Graduated cylinder
• Burette
• Pipette

Every substance has unique or characteristic properties. 

These properties can be classified into two categories – 

Physical properties and chemical properties. 

Physical properties are those properties which can be measured or observed without changing the identity or the composition of the substance. 

E.g. colour, odour, melting point, boiling point, density etc. 

The measurement or observation of chemical properties requires a chemical change to occur. e.g. Burning of Mg-ribbon in air 

Chemical properties are characteristic reactions of different substances; these include acidity or basicity, combustibility etc.Many properties of matter such as length, area, volume, etc., are quantitative in nature. Metric System was based on the decimal system. 

The International System of Units (SI) 

The International System of Units (in French Le System International d‘Unites– abbreviated as SI) was established by the 11th General Conference on Weights and Measures (CGPM from Conference Generale des Poids at Measures). The SI system has seven base units.

Correct option is (a) 24 g of C (12)

Correct option is (a) 36 g of water

Azidothymidine.

• Measurement involves comparing a property of matter with some fixed standard which is reproducible and unchanging.
• Properties such as mass, length, area, volume, time, etc. are quantitative in nature and can be measured.
• A quantitative measurement is represented by a number followed by units in which it is measured.
• These units are arbitrarily chosen on the basis of universally accepted standards. e.g. Length of class room can be expressed as 10 m. Here, 10 is the number and ‘m’ is the unit ‘metre’ in which the length is measured.

AZT is Azidothymidine. It is lifesaving drug and is used for helping AIDS victims.

Matter is anything which has mass and occupies space. However, material corresponds to the matter which has specific uses. e.g., glass, cement etc.

Azidothymidine (AZT)

Cisplatin and Taxol

(i) Number of atoms in 1 g of Au = {197}/{6.022 x 10²³} = 32.7 x 10^-23

(ii) Number of atoms in 1 g Na = {2.3}/{6.022 x 10²³} = 3.82 x 10^-23

(iii) Number of atoms in 1 g of Li = {7}/{6.022 x 10²³} = 1.16 x 10^-23

(iv) Number of atoms in 1 g Cl₂ = {35.5}/{6.022 x 10²³} = 5.89 x 10^-23

1 g gold will have the largest number of atoms.

(a) Cisplatin 

(b) Taxol.

(i) 28.7 pm = 2.87 x 10^-11 pm

(ii) 15.15 pm = 1.515 x 10^-11

(iii) 25365 mg = 25365 x 10^-3 g = 25365 x 10^-6 kg = 2.5365 x 10^-2 kg

Atoms and molecules.

B) liberate CO₂ during respiration

C) Food poisoning