Revision Series | Science and Tech | Optics – 2 | 114

ANSWER: B

• The intensity of scattered light is inversely proportional to its wavelength and the wavelength of violet and blue is low, thus they scattered more. This is the main cause for the blue colour of the sky.
• As we know that sunlight consists of seven colours, of these, red has the maximum wavelength. During sunrise and sunset, the rays have to travel a larger part of the atmosphere because they are very close to the horizon. Therefore light other than red is mostly scattered away. Most of the red light which is least scattered enters our eyes. Hence, the sun appears red.
• The rainbow is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing

ANSWER: A

When the position of object is between infinity and pole (P) of the convex mirror, then the image will be formed between the pole (P) and the focus (F) behind the mirror.

The image thus formed is diminished, virtual and erect.

ANSWER: B

• Visible light is that part of electromagnetic radiation which can be seen by human eyes.
• Visible light is usually defined as having wavelengths in the range of 400-700 nm (4000-7000 A) between the infrared and ultraviolet.
• A typical human eye will respond to wavelengths from about 380 to 750 nm.
• The electromagnetic spectrum encompasses all type of radiations.
• The part of the spectrum that reaches earth from the sun is between 100 nm to 10^6 nm.
• This band is broken into three ranges – Infrared (above 700 nm), Visible (400 to 700 nm), Ultraviolet (below 400 nm.

Answer: A

• Concave mirror is used in the headlights of cars and in searchlights.
• A light placed at the focus of a concave lens can form a parallel beam and is used in car headlights and searchlights.

Answer: A

• Statement (1) is true. The coin will appear to be closer than it really is due to the refraction of light, In this case, the ray that is coming to the eyes is traveling from denser medium (water) to the rarer medium (air).
• The statement (2) is also true. If a person underwater looks at a coin above the water surface the coin will appear to be at a higher level than it really is also due to the retraction of light. In this case, the ray is travelling from the rarer medium to denser medium.

ANSWER: D

Head Mirror is mostly used by doctors for the examination of ear, nose, and throat. It comprises a circular concave mirror, with a small hole in the middle and is attached to a head-band. Hence statement (d) is not correct. Remaining Statements are correct.

ANSWER: C

Answer: D

Due to the refraction of light, the sun is visible to us a few minutes before sunrise and a few minutes after sunset

Answer: D

Answer: C

An air bubble in water, whose surface is convex will act like a concave lens (divergent lens). The refractive index of water is more than that of air. Thus the nature of lens of submerged water bubble is changed.

Answer: B

Bonn Convention came into exist for the conservation of migratory species of wild animals. And also to conserve terrestrial species and marine species throughout their range was the objective of this convention.

Answer: C

CITES was conceptualized in 1963 at a meeting of the (IUCN) International Union For Conservation Of Nature. It came into force in 1975 and consists of 183 member countries to date that abide by CITES regulations by implementing legislation within their own borders to enforce those regulations. Located in Geneva, Switzerland, the CITES is administered by the United Nations under its UNEP (United Nations Environment Programme) Wing.

Answer: C

The Kyoto Protocol is an international treaty that extends the 1992 United Nations Framework Convention on Climate Change (UNFCCC) that commits state parties to reduce greenhouse gas emissions. The Kyoto Protocol was adopted in Kyoto, Japan, on 11 December 1997 and entered into force on 16 February 2005

Answer: D

Ramsar Convention was signed in 1971 in the Ramsar city of Iran. It is an international treaty for ‘conservation and sustainable use of wetlands’ and is hence also known as the Convention on Wetlands.

Answer: D

Flipflopi the world’s first sailing boat made entirely from plastic waste, aims to raise people’s awareness of plastic pollution in oceans. Flip-flops were collected from beaches and towns on the Kenyan coast. The Flip Flop project is a positive African plastic revolution. The Flipflopi is a Kenyan community-built boat constructed from recycled marine plastic and flip-flops. The project calls for a plastic revolution and raises awareness of the dangers of single-use plastic, of which 12 million tonnes are dumped at sea every year rather than repurposed or recycled.