Explanation:

The Raman Spectroscopy
Raman spectroscopy is an analytical technique where scattered light is used to measure the
vibrational energy modes of a sample.
In 1928, Raman discovered that when a stream of light passes through a liquid, a fraction of the
light scattered by the liquid is of a different colour.
While Raman was returning from London in a 15-day voyage, he started thinking about the
colour of the deep blue Mediterranean.
He wasn’t convinced by the explanation that the colour of the sea was blue due to the reflection
of the sky.
As the ship docked in Bombay, he sent a letter to the editor of the journal Nature, in which he
penned down his thoughts on this.
Subsequently, Raman was able to show that the blue colour of the water was due to the
scattering of the sunlight by water molecules.
By this time he was obsessed with the phenomenon of light scattering.
How does it work?
The Raman Effect is when the change in the energy of the light is affected by the vibrations of
the molecule or material under observation, leading to a change in its wavelength.
Significantly, it notes that the Raman effect is “very weak” — this is because when the object in
question is small (smaller than a few nanometres), the light will pass through it undisturbed.
But a few times in a billion, light waves may interact with the particle. This could also explain
why it was not discovered before.
In general, when light interacts with an object, it can either be reflected, refracted or
transmitted.
One of the things that scientists look at when light is scattered is if the particle it interacts with
is able to change its energy.
Applications
Raman spectroscopy is used in many varied fields – in fact, any application where non-
destructive, microscopic, chemical analysis and imaging is required.
Whether the goal is qualitative or quantitative data, Raman analysis can provide key information
easily and quickly.
It can be used to rapidly characterize the chemical composition and structure of a sample,
whether solid, liquid, gas, gel, slurry or powder.
Rainbow is formed due to Dispersion and Total Internal Reflection

Explanation:

Winter-grade diesel

Motorists in high-altitude sectors like Ladakh, Kargil, Kaza and Keylong face the problem of
freezing of diesel in their vehicles when winter temperatures drop to as low as -30o
Indian Oil has come up with an innovative solution to this problem by introducing a special
winter-grade diesel with a low pour-point of -33o
This fuel does not lose its fluidity function even in extreme winter conditions.
This will help reduce the hardships faced by the local people for transportation and mobility
during the harsh winter months.
It will further facilitate the local economy as well as tourism of the region.
It has lower sulphur content, which would lead to lower deposits in engines and better
performance.

Explanation:

Foreign exchange reserve: then and now in terms of grains
In the mid-1960s the country had about $400 million.
If India had spent all its foreign currency reserves just on wheat imports, it could have
imported about seven million tonnes (mt) of wheat.
Today, India has foreign exchange reserves of more than $500 billion.
Even if the country has to buy 20 mt of wheat at a landed cost of $250/tonne, it will spend just
$5 billion it is just one per cent of its foreign exchange reserves.
In that sense, the biggest reform in the last three decades that has led to “aatma nirbharta” in
food is the correction of the exchange rate.
Another factor is coupling and the gradual integration of India with the world economy.
This has helped India increase its foreign exchange reserves from $1.1 billion in 1991 to more
than $500 billion today.
India: Net exporter of agricultural products
India has been the net exporter of agricultural products ever since the economic reforms began
in 1991.
The golden year of agri-trade was 2013-14 when net agricultural trade surplus was $24.7 billion.
In 2019-20, agri-exports were just $36 billion, and the net agri-trade surplus at $11.2 billion.
With this dull performance doubling agri-exports by 2022 looks almost impossible.
Let’s look at what India exports
Marine products with $6.7 billion exports top the list.
The second is rice at $6.4 billion of which basmati is at $4.6 billion and common rice at $2.0
billion.
Next is spices at $3.6 billion.
Other items are buffalo meat at $3.2 billion, sugar at $2.0 billion, tea and coffee at $1.5 billion,
fresh fruits and vegetables at $1.4 billion, and cotton at $1 billion.

Sindhu Darshan Puja.

Sindhu Darshan Festival is a festival of India held every year on full moon day (on Guru
Purnima) in the month of June.
It is held at Leh, in Ladakh District of Ladakh. It stretches for three days.
It was first started in the October by veteran politician L.K. Advani, 1997 and continues to be
held every year since then, attracting large number of foreign and domestic tourists.
The main reason behind the celebration of Sindhu Darshan Festival is to endorse the Indus
River (Sindhu River) as an icon of the communal harmony and unity of India.

Other Festival:

Hemis Festival.
Thiksey, Karsha and Spituk Gustor.
Stok Guru Tsechu Festival.
Phyang Tsedup Festival.
Yuru Kabgyat Festival.
Sindhu Darshan (Visit Indus) Festival.
Ladakh Harvest Festival.
Tak -Tok Festival.

Explanation: Legal tender money is a type of payment that is protected by law.
Legal tender is also known as forced tender which is very secured and it is impossible to deny the legal tender while subsiding a debt which is assigned in the same medium of exchange. In other words we can say that the term legal tender does not represent the money itself, rather it is a kind of status which can be bestowed on certain types of money.
The options given in the Question does not properly explain the definition of legal tender money. So, therefore the most suitable explanation is answer b.