“Silver Acetate
• Silver is known to have antibacterial property but
it may not be used due to its toxicity.
Hence, statements 1 and 2 are correct.
• However, when silver acetate was incorporated
in the hydrogel the toxicity was reduced and thus
suitable for treating bacterial infections.
• The hydrogel with the presence of silver reduces
the cell size of the E.coli and disrupts its cell
membrane, leading to leakage of cellular contents.
• The hydrogel containing silver acetate was found
to be non-toxic to normal kidney epithelial cells
and red blood cells.”

“Choose the correct statement/s from those given below.
1. Sol is a colloid in which the particles are solid and the dispersion medium is fluid.
2. They display the Tyndall effect.” “Sol
• Sol is a colloid (aggregate of very fine particles
dispersed in a continuous medium) in which the
particles are solid and the dispersion medium is fluid.
• If the dispersion medium is water, the colloid may
be called a hydrosol and if air, an aerosol.
• They do not settle or separate over time
• They display the Tyndall effect.
€ Tyndall effect is a phenomenon of scattering of
a beam of light by a medium containing small
suspended particles – e.g., smoke or dust in a
room, which makes visible a light beam entering
a window.
€ This effect is exhibited by all colloidal solutions
and some very fine suspensions. Therefore, it can
be used to verify if a given solution is a colloid.”

“Cancer Incidence in India
• According to the study, as India continues to age,
cancer cases will double every 20 years.
• Uttar Pradesh, Bihar, Jharkhand and Odisha, will bear
the biggest cancer burden in the next 10-20 years.
• According to Epidemiological Transition Level
concept (ETL), number of patients with cancer
started to increase as the life expectancy of Indians
started to increase.
• The States with high ETL have a better development
index and higher cancer rates.
€ ETL is highest in Kerala and is lowest in Uttar
Pradesh.
• Government should consider Bhore committee and
Mudaliar committee report recommendations for
cancer that include creation of a multidisciplinary
cancer treatment unit in all medical colleges and
setting up of a stand-alone cancer speciality hospital.”

“Why in news?
Recently, researchers have found Mexico’s prickly
pear cactus, that can play a new and innovative role in
the production of biodegradable plastics.
• The pulp for the cactus is strained to obtain a juice
and is then mixed with non-toxic additives to produce
sheets that can be used to form different types of
packaging.
• It can provide a solution to one of the world’s biggest
pollution conundrums i.e., Plastic pollution.
• UN is committed to significantly reduce single-use
plastics over the next decade. In pursuance of this
India also seeks to ban single-use plastics.
€ Single-use plastics are disposable plastic items
that are commonly used for packaging and include
items intended to be used only once before they
are thrown away or recycled.”

“Why in news
USA’s space agency NASA is planning to
launch the James Webb Space Telescope (JWST)
in 2021, which will use a natural phenomenon
called “gravitational lensing” to carry out
astronomical observations.

Gravitational Lensing
• The phenomenon of gravitational lensing occurs
when a huge amount of matter, such as a massive
galaxy, cluster of galaxies or a black hole, creates
a gravitational field that distorts and magnifies the
light from objects behind it.
• Gravitational lensing is based on Einstein’s theory of
general relativity (Mass bend light).
Hence, statement 1 is correct.
• Normal lenses such as the ones in a magnifying glass
work by bending light rays that pass through them in
a process known as refraction, in order to focus the
light somewhere else.
• Similarly, the gravitational field of a massive object
causes light rays passing close to that object to be
bent and refocused somewhere else.
Hence, statement 2 is correct.
• The more massive the object, the stronger its
gravitational field and hence the greater the bending
of light rays – just like using denser materials to
make optical lenses results in a greater amount of
refraction.
• In effect, gravitational lenses act like natural cosmic
telescopes.
Hence, statement 3 is correct.”

“Nicotine
• Nicotine is a plant alkaloid that contains nitrogen,
which is found in several types of plants,
including the tobacco plant and can also
be produced synthetically.
Hence, statement 1 is correct.
• Nicotine is both a sedative and a stimulant.
• Nicotine is used as a direct substance
in e-cigarettes and the content ranges
up to 36 mg/mL. Although regular cigarettes have
nicotine, but it ranges between 1.2 to 1.4 mg/mL.
• Chewing or snorting tobacco products usually releases
more nicotine into the body than smoking.
Hence, statement 2 is correct.

Harmful Effect of Nicotine
• Nicotine on direct application in humans causes
irritation and burning sensation in the mouth and
throat, increased salivation, nausea, abdominal pain,
vomiting and diarrhea.
• It also increases pulse rate and blood pressure.

Classification of Poison
US Department of Transport divides poisons in two
classes.
• Class-A: Highly toxic chemicals which even in very
small quantities as gas or vapor in air are dangerous
to life such as cyanogen, hydrocyanic acid, nitrogen
peroxide, and phosgene.
• Class-B: Chemicals other than those included in Class-A
and comparatively less toxic but considered dangerous.”

“Why in news?
Recently, the Chandrayaan-2’s orbiter has scanned
a crater on the moon named after 20th century’s acclaimed
radio physicist Sisir Kumar Mitra.
• The set of images taken by the Chandrayaan-2, also
include the images of impact craters namely:
€ Jackson: Named after a Scottish astronomer.
€ Mach: Named after an Austrian physicist and
philosopher.
€ Korolev: Named after the father of the space
programme of the erstwhile USSR.”

“Solar and Lunar Eclipse
Solar eclipses occur when the Sun, Moon and earth
all fall in the same line so that the Moon passes
between Earth and the Sun, leaving a moving region
of shadow on Earth’s surface.
Hence, statement 1 is correct.
• Lunar eclipses occur when the Sun, Moon and earth
all fall in the same line and Earth passes between the
Sun and the Moon, casting a shadow on the Moon.
• Eclipses may be classified into 4 types i.e. Annular,
Total, Partial and Hybrid.
• The type of eclipse we experience depends on the
type of shadow that is involved.
€ Both the Moon and Earth cast 3 shadows: umbra,
penumbra, and an antumbra.
• The umbra is a shadow’s dark core. The light
source is not visible and the object blocks all
direct light rays.
• The penumbra is a half-shadow that occurs
when a light source is only partly covered by
an object.
• Antumbra – the lighter part of the shadow
that begins where the umbra ends.
Hence, statement 2 is correct.”

“X-Rays
• X-rays are a form of high-energy electromagnetic
radiation. X-radiation is referred to as Röntgen
radiation, after the German scientist Wilhelm
Rontgen who discovered these in 1895.
Hence, statement 1 is correct.

Soft and Hard X-rays
• X-rays are usually described by their maximum
energy, which is determined by the voltage between
the electrodes.
• X-rays with high photon energies (above 5–10 keV)
are called hard X-rays.
Hence, statement 2 is correct.
€ Due to their penetrating ability hard X-rays
are widely used to image the inside of visually
opaque objects.
Hence, statement 3 is correct.
• Those with lower energy (and longer wavelength)
are called soft X-rays.”

“Haemophilia A
• Hemophilia A (also called factor VIII (FVIII) deficiency
or classic hemophilia), is a genetic disorder caused
by missing or defective factor VIII, a clotting protein.
• Although it is passed down from parents to children,
about 1/3 of cases are caused by a spontaneous
mutation, a change in a gene.
• The gene for hemophilia is carried on the X
chromosome. Hemophilia is inherited in an X-linked
recessive manner.
Hence, statement 1 is correct.
• Females inherit two X chromosomes, one from
their mother and one from their father (XX). Males
inherit an X chromosome from their mother and a Y
chromosome from their father (XY).
• That means if a son inherits an X chromosome carrying
hemophilia from his mother, he will have hemophilia.
It also means that fathers cannot pass hemophilia
on to their sons.
Hence, statement 2 is incorrect.
• But because daughters have two X chromosomes, even
if they inherit the hemophilia gene from their mother,
most likely they will inherit a healthy X chromosome
from their father and not have hemophilia.
• A daughter who inherits an X chromosome that
contains the gene for hemophilia is called a carrier.
She can pass the gene on to her children. Hemophilia
can occur in daughters, but is rare.
Hence, statement 3 is incorrect.
• Symptoms: People with hemophilia A often, bleed
longer than other people. Bleeds can occur internally,
into joints and muscles, or externally, from minor
cuts, dental procedures or trauma. ”

“Why in news
According to Scientists, the study of gynandromorphs
could offer clues as to why some human diseases
strike one gender more than the other.

• Gynander or gynandromorphs are the organisms in
which the body consists of both male and female parts.
Hence, statement 1 is correct.
• The term is derived from the Greek words (gyne =
woman; aner = man and morphe = form). Thus, in
these animals one part of the body shows female
and the other part male features. The phenomenon
has been documented in birds, crustaceans and
butterflies.
Hence, statement 2 is correct.
• However, it still remains a mystery as to how
gynandromorphs are born. Gynandromorphs occur
naturally, usually resulting from a random genetic error.
Hence, statement 3 is correct.
• These instances of split-sex animals and insects could
offer clues to why some human diseases strike one
sex more than the other.
• Diseases like multiple sclerosis, obesity, metabolic
syndrome, autoimmune disease, Alzheimer’s, even
ageing differs by sex. Few decades back, scientists
did not think that sex chromosomes played any role
in causing sex differences in these diseases.”

“Choose the correct statement/s from those given below.
1. Total internal reflection occurs if the angle of incidence is greater than critical angle.
2. Glass prisms can be shaped to produce total internal reflection.” “• Total internal reflection is a complete reflection of a
ray of light within a medium such as water or glass
from the surrounding surfaces back into the medium.
• The phenomenon occurs if the angle of incidence is
greater than a certain limiting angle, called the critical
angle.
Hence, statement 1 is correct.
• Glass prisms can be shaped to produce total internal
reflection and as such are employed in binoculars,
periscopes, telescopes, and other optical instruments.
Hence, statement 2 is correct.
• Light rays may be conducted over long, twisting paths
by multiple total internal reflection in glass or plastic rods
or fibres.”

“• In optics, dispersion is the phenomenon in which
the phase velocity of a wave depends on its frequency.
Media having this common property may be termed
dispersive media.
• In optics, one important and familiar consequence of
dispersion is the change in the angle of refraction of
different colors of light, as seen in the spectrum produced
by a dispersive prism and in chromatic aberration of lenses.
• The most familiar example of dispersion is probably a rainbow,
in which dispersion causes the spatial separation of a white
light into components of different wavelengths (different colors). ”

“• Interference is a phenomenon in which two waves
superpose to form a resultant wave of greater, lower,
or the same amplitude.
Hence, statement 1 is correct.
• Constructive and destructive interference result from the
interaction of waves that are correlated or coherent with
each other, either because they come from the same source
or because they have the same or nearly the same frequency.
• Interference effects can be observed with all types of waves,
for example, light, radio, acoustic, surface water waves,
gravity waves, or matter waves.
The resulting images or graphs are called interferograms.
Hence, statement 2 is correct.”

“• Newton’s laws of motion are three physical laws that,
together, laid the foundation for classical mechanics.
• They describe the relationship between a body and
the forces acting upon it, and its motion in response to
those forces.
• More precisely, the first law defines the force qualitatively,
the second law offers a quantitative measure of the force,
and the third asserts that a single isolated force does not exist.
• These three laws have been expressed in several ways,
over nearly three centuries, and can be summarised as follows:
– First law
In an inertial frame of reference, an object either remains at
rest or continues to move at a constant velocity, unless
acted upon by a force.
Hence, statement 1 is correct.
– Second law
In an inertial frame of reference, the vector sum of the forces F
on an object is equal to the mass m of that object multiplied
by the acceleration a of the object: F = ma.
(It is assumed here that the mass m is constant).
Hence, statement 2 is incorrect.
– Third law
When one body exerts a force on a second body, the second
body simultaneously exerts a force equal in magnitude and
opposite in direction on the first body.
Hence, statement 3 is incorrect.”