BIOLOGY-----
1.perbrine is caused by......?
2.why cu-T acts as an effective contraceptive?
3.why is lac operon'scalled as a negative regulation system?
PHYSICS----
1.name the electromagnetic radiation used for viewing objects through haze and fog?
2.what should be the energy bandgap range of semiconductor used for fabrication of visible LEDs?
3.why are the sky waves not used in the transmission of TV signals?
plz I request you know then do these but if u don't know then plz don't do bcoz it is very very important for me...
plz HS passed seniors help me to do these....
Answers
1. Electromagnetic radiation used for viewing objects through haze and fog is the Infrared radiation. The wavelength of Infrared radiation is just higher than that of visible red light. Even visible red light is used for seeing through haze and fog as red light is less scattered by the particles suspended in air.
Reason is that the red and infrared light are less scattered by suspended particles like dust or pollution in air.
2. Energy band gap approximately is given by the law E = h f
f ranges from 430 THz (red light) to 770 THz (violet light)
h = 6.67 * 10⁻³⁴ J-s.
Multiply h and f to get approximate range of energy gap.
When electrons get excited from lower energy level to the higher energy level with this band gap and then jump back to their stable energy level, they emit electromagnetic radiation with energy equal to the band gap.
3. Sky waves have a range of 2 MHz to 30 MHz range. They can get reflected from the Ionosphere around Earth , from 400 km above EArth's surface.
However the TV signals range from 80 MHz to 300 MHz or even more. This is the range of signals required for seeing a good quality picture. They will pass through the Ionosphere to troposphere. They can get reflected from troposphere. The TV signals are called space waves.
So sky waves cannot be used for transmission of TV signals.
Biology:
Copper T or Cu T or Copper IUD (intrauterus device) is a device for prevention of pregnancy. It is used by women. Cu T is inserted into the uterus. It is in the shape of a T. It functions by killing the sperms from the male. The presence of copper in it increases its effectiveness by increasing the copper ions, prostaglandins and white blood cells. It is good for health.
It is good for about 3 to 8 years. It is cheap and effective. Though there are side effects, it is recommended. It can be removed when pregnancy is desired.
Perbrine is a disease affecting silworms. It is also called pebrine or pepper disease.
It is an infection caused by parasites (single celled microsporidia). These
parasites are non-photosynthetic and live on the hosts. The parasites could be amoebae,
ciliates, fungi etc. This disease is
caused in silkworms in their larva stage in general. The eggs of silkworms are infected
by the parasites. So the disease is transmitted on to next generation. Due to
that many silkworms die in their infancy. They are unable to spin any silk
thread. Their physical appearance indicates that they are affected by pebrine.
For the silkworm culture specialists, it is important to keep their silkworm out of pebrine.
Lac Operon:
The lacl gene is the gene that regulates the lac operon. It is the lac repressor. Lacl gene induces a negative regulation in the lac operon. The lac repressor protein turns of the gene if a lactose molecule is not added for transcribing the gene. The repressor protein blocks RNA polymer binding (attaching) to the promoter. It means that the transcription of the gene into a messenger RNA is prevented.
Since the regulation prevents gene from decoded it is a negative regulatory system.