SA I - Full Physics Test 2 - Class 10 MCQ

The power of a lens is the reciprocal of its focal length. It is a measure of the degree of convergence or divergence of light rays achieved by a particular lens. The power of a convex lens is positive.

Given, focal length = 40 cm or 0.40 m

Therefore, Power of the given convex lens

A convex lens (converging lens) is thicker at the middle than at the edges. A concave lens (diverging lens) is thicker at the edges than at the middle.

• Amrita Devi Bishnoi is still remembered with reverence for the way she fought for protecting the khejri trees in Khejrali village. She; along with 363 other people; sacrificed her life for the protection of khejri trees in 1731.
• Sunderlal Bahuguna (born 9 January 1927) is a noted Garhwali environmentalist, Chipko movement leader and a follower of Mahatma Gandhi's philosophy of Non-violence and Satyagraha. This idea of chipko movement was of his wife and the action was taken by him.
• A K Banerjee was a real visionary. He involved the local people in the revival of 1,272 hectares of forest. In lieu of that the villagers were given employment in silviculture and harvest and were given 25% of the harvest. They were also allowed to gather firewood and fodder against a nominal payment. Due to active participation of the local community there was remarkable revival of the Arabari sal forest. By 1983, the value of the forest rose to Rs. 12.5 crores.
• Panduranga Hegde is an environmentalist from Uttara Kannada district, Karnataka, India and is known as the person who started Appiko movement to protect trees in Western Ghats.

Retina works like a screen or camera film. Retina is full of light and colour sensitive cells. These cells, upon receiving image send electrical signals to the brain, which processes these information to make a mental image of what we see.

The SI unit of electric current is ampere (symbol A). It is named after the French scientist - Andre Marie Ampere. The ohm (symbol Ω) is the SI unit of electrical resistance, named after German physicist - Georg Simon Ohm. The SI unit of potential difference is volt (symbol V), named after the Italian physicist - Alessandro Volta. The SI unit of resistivity is ohm-metre (symbol Ω-m).

Power of accommodation: The ability of the eye to focus both near and distant objects, by adjusting the focal length of the eye lens, is called the accommodation of the eye

Near point: It  is  25cm  for  normal  eye.  The minimum distance at which object can be seen most distinctly without strain.

Far point: It  is  infinity  for  normal  eye.  It  is  the farthest  point  upto which  the  eye  can see object clearly.

Least distance of distinct vision in old people: As the person grows old, his ciliary muscle responsible for adjusting the eye lens gets weakened. As a result the power of accommodation reduces and hence the least distance of distinct vision for old people generally increases.

Cataract: The image can not be seen distinctly because eye lens become milky and cloudy.

Myopia (Near Sightedness): A person can  see nearby object clearly, but cannot  see distant object distinctly. Image formed in front of the retina.

Hypermetropia  (Far-Sightedness): A person cannot  see nearby object clearly, but can  see distant object distinctly. Image  formed at a point behind  the  retina.

Presbyopia: As we become old,  the power of accommodation of  the eye usually decreases (due to weakening of cilliary muscles), the near point gradually  recedes away. This defect is called Presbyopia. Person may suffer from both myopia and hypermetropia.

A Rheostat is an electrical instrument used to control current in a circuit by varying the resistance. The resistance can be decreased or increased with the help of a rheostat.

Twinkling of stars is due to atmospheric refraction.

The rainbow is a formed due  to  the dispersion and total internal reflection of  sunlight by  the  tiny water droplet, present  in atmosphere.

The rising sun appears red because the sun  is near horizon, and  therefore  the sunlight has to travel larger distance in atmosphere which scatters away most of the blue light (shorter wavelength) by the atmospheric particles.

The phenomenon of scattering of light by the colloidal particles is known as Tyndall Effect. Light of all wave lengths are scattered equally by the clouds and hence clouds appears white.

In an electric circuit, the direction of electric current is from the positive terminal of the battery to the negative terminal of the battery. This is as per convention. Electrons were not known at the time when the phenomenon of electricity was first discovered. Electric current was considered to be the flow of positive charges and the direction of flow of positive charges was taken to be the direction of electric current.

(1) The group of solar cells joined together in definite pattern is solar panel---Solar panels are those devices which are used to absorb the sun's rays and convert them into electricity or heat. Description: A solar panel is actually a collection of solar (or photovoltaic) cells, which can be used to generate electricity through photovoltaic effect
(2) The device used for obtaining energy for flowing water is water wheel----A water wheel is a machine for converting the energy of flowing or falling water into useful forms of power, often in a watermill
(3) A barrier constructed on the river to store the flowing water is dam---A dam is usually constructedacross a river to create a reservoir in the valley behind by storing the water that flows into it naturally. ... Small rivers and streams are usually diverted through a tunnel, or a channel that is constructed around the side of the dam
(4) A domestic fuel which contains butane is LPG---Liquefied petroleum gas or liquid petroleum gas (LPG or LP gas), also referred to as simply propane or butane, are flammable mixtures of hydrocarbon gases

The lateral displacement of an incident ray passing out of a rectangular glass slab is directly proportional to the thickness of glass slab, angle of incidence, and refractive index however it is inversely proportional to the wavelength of incident light.

(1) Nuclear energy is the energy obtained from the nucleus of an atom---the energy released during nuclear fission or fusion, especially when used to generate electricity.
(2) Geothermal energy is the energy present inside the earth's crust----Geothermal energy is the heat from the Earth. It's clean and sustainable. Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth's surface, and down even deeper to the extremely high temperatures of molten rock called magma
(3) Fission occurs by breaking of heavy nucleus into two medium sized nuclei---A schematic nuclear fission chain reaction. 1. A uranium-235 atom absorbs a neutron and fissions into two new atoms (fission fragments), releasing three new neutrons and some binding energy
(4) Nuclear fusion occurs when two light weight nuclei combine to from a big nuclei----nuclear fusion is a reaction in which two or more atomic nuclei come close enough to form one or more different atomic nuclei and subatomic particles (neutrons or protons). The difference in mass between the products and reactants is manifested as the release of large amounts of energy.

'All of these ' option1 is correct because option  2.Pollen is found naturally in the air, human activities and choices can increase the amount of pollen in our air, and in turn, can cause people to have more severe allergic reactions.

Option 3.Volcanic eruptions release large quantities of greenhouse gases and other aerosols into the atmosphere which causes pollution

Option 4. The burning of fossil fuels to produce energy also releases significant amounts of carbon dioxide and other greenhouse gases into the environment

When light enters from one medium into another, the frequency of light does not change. Speed, wavelength and amplitude may change depending upon the optical density of the two mediums.

Early organisms are known as cyanobacteria, or blue-green algae. These microbes conduct photosynthesis: using sunshine, water and carbon dioxide to produce carbohydrates and, yes, oxygen. 

In fact, all the plants on Earth incorporate symbiotic cyanobacteria (known as chloroplasts) to do their photosynthesis of early days where no oxygen is present to this day.

LPG is a good fuel with high calorific value, burns with a smokeless flame, does not produce any poisonous gases on combustion and do not cause pollution

The virtual image formed by a plane mirror is virtual, erect and of the same size as that of the object. According to New Cartesian Sign Convention, the focal length (and power) of a convex lens is positive, and that of a concave lens is negative. A concave lens always produces erect and virtual images. A convex mirror always forms virtual images that are erect and diminished. The focal length of a convex mirror is positive, and that of a concave mirror is negative. A convex lens produces real and enlarged images when the object is placed beyond the centre of curvature.

An ammeter has a low resistance since it is always connected in series in an electrical circuit. If it is connected in parallel, a high current will flow through it and it is likely to burn out.

Refraction is the phenomenon of change in the direction of propagation of light when it passes from one transparent medium into another. Reflection is the phenomenon of bouncing of light from the interface of an opaque medium. When a ray of light passes from a denser medium to a rarer medium, the velocity of light increases. When a ray of light passes from a rarer medium to a denser medium, the velocity of light decreases.

In myopia, a person can  see nearby object clearly, but cannot  see distant object distinctly. Image formed in front of the retina.

It is due to: 

1. Elongation of  the eye ball
2. Excessive curvature of eye  lens  (thick eye lens→ decrease in focal  length→ increase in power of lens)

An ammeter is always connected in series in an electric circuit. It is likely to burn out if connected in parallel.

An image formed by a plane mirror is always erect, virtual and of the same size as that of the object. A convex mirror always forms an erect, virtual and a diminished image, for any position of the object.

Given, potential difference across the conductor, V = 0.8 V ; current flowing through the conductor = 0.2 A

According to Ohm's law, the resistance of the conductor is given by:

Therefore,

The energy released during nuclear fission or fusion, especially when used to generate electricity. This does not include any action of solar energy.