Why Rajasthan and Gujarat Receive less rainfall ??

Posted on May 21, 2015

1) This is because the Aravali Range in Rajasthan lie parallel to the Arabian Sea branch of South West Monsoon, and do not offer any obstruction to the rain bearing winds. By the time, the Bay of Bengal branch of the South West Monsoon reaches to the western part of the country i.e. Gujarat and Rajasthan it do not have sufficient moisture left with to cause rain. Also the same Aravali Range which fails to act as a barrier to the Arabian sea branch, act as a barrier for the Bay of Bengal branch of Monsoon and limit its reach to the eastern side of Aravali i.e. M.P. and Maharashtra.

2) The second reason is that the hot climate of Rajasthan increases the moisture holding capacity of the rain bearing winds, and does not allow it to shed its moisture in Rajasthan.

Difference Between Radar and Sonar

Posted on May 6, 2015 Updated on May 7, 2015

Radar vs Sonar
RADAR and SONAR are both detection systems used to identify objects and their position related parameters when they are at a distance and not directly observable. RADAR stands for RAdio Detection and Ranging, and SONAR stands for SOund Navigation And Ranging. Both detection systems use the method for detection of the reflection of a transmitted signal. The type of the signal used in the system makes all the difference; RADAR uses radio waves, which are electromagnetic waves and SONAR uses acoustic or sound waves, which are mechanical waves.

How Radar Works
Radar sets, also called radar systems, come in many different sizes, depending on the job they are expected to do. But all have four main parts — a transmitter, an antenna, a receiver, and an indicator (display screen). The transmitter produces the radio waves. When a radio wave strikes an object such as an airplane, part of the wave is reflected back to the radar set. The signal is detected by the antenna as a radio echo. The returning echo is sent to the receiver, where its strength is increased, or amplified. The echo is usually displayed as an image that can be seen on the indicator.
A common type of radar is called pulse radar. This type of radar sends out radio waves in short bursts, or pulses. The distance to a target is determined by the time it takes the signal to reach the target and the echo to return. Radio signals travel at a known speed — about 186,000 miles (300,000 kilometers) per second, the speed of light. If the radio signal comes back in 1/1,000 second, then the round trip is 186 miles (300 kilometers). The target must be half that far, or 93 miles (150 kilometers) away.
Pulsed transmission helps determine the distance more accurately. Why is this so? Imagine that you are about to shout across a canyon to make an echo. If you shout a long sentence, the first words will come back before you can finish. It would be impossible to hear the entire echo clearly because it would be mixed with your own speech. But if you shout a short word the echo comes back crisp and clear with no interference from the transmitter (you).

How Sonar Works
There are two types of sonar sets: active and passive. An active sonar set sends out sound pulses called pings, then receives the returning sound echo. Passive sonar sets receive sound echoes without transmitting their own sound signals.In active sonar sets, the sound signals are very powerful compared with ordinary sounds. Most sonar sets send out sounds that are millions of times more powerful than a shout. Each ping lasts a fraction of a second.
Some sonar sets emit sounds you can hear. Other sonar signals are pitched so high that the human ear cannot hear them. These signals are called ultrasonic waves. (“Ultra” means “beyond,” and “sonic” means “sound.”) The sonar set has a special receiver that can pick up the returning echoes. The location of underwater objects can then be determined by the length of time that elapses between sending the signal and hearing the returning echo.

Tomato Blight: How to Identify and Treat Early Blight in Tomatoes

Posted on May 3, 2015

Tomato blight, in its different forms, is a disease that attacks a plant’s foliage, stems, and even fruit.

Early blight (one form of tomato blight) is caused by a fungus, Alternaria solani, which over-winters in the soil and infected plants. Affected plants underproduce. Leaves may drop, leaving fruit open to sunscald.

Early blight’s Latin name is sometimes confused with a form of tomato rot, alternaria, a different tomato problem altogether. To muddle matters further, early blight is occasionally mistaken for Septoria leaf spot because the two diseases infect tomatoes at the same time.

What does early blight look like?

Photo: University of Minnesota Extension

• Dark, concentric spots (brown to black), ¼ – ½” in diameter, form on lower leaves and stems. Early blight is marked by tell-tale rings.
• Fruit can also be affected; spots often begin near stem of fruit
• Lower leaves turn yellow and drop

When does early blight affect plants?

• It’s most evident during early- to mid-season
• It’s most common in humid weather
• It often strikes after a period of heavy rainfall

How do you control and treat early blight?

• The best control measure for tomato blight is prevention (see below).
• Remove and destroy infected leaves (be sure to wash your hands afterwards).
• Treat organically with copper spray, which you can purchase online, at the hardware store, or home improvement center. Follow label directions. You can apply until the leaves are dripping, once a week and after each rain.
• Once blight is present and progresses, it becomes more resistant to biofungicide and fungicide. Treat it as soon as possible and on a schedule.
• Treat organically with a biofungicide like Serenade to lessen symptoms. Follow label instructions. Or apply a fungicide such as chlorothalonil (sold as Fungonil), Mancozeb fungicide, or Daconil at the first sign of blight when fruit sets (as a preventative measure) or when conditions indicate a strong potential for it to develop. Follow label directions. Re-apply every 7-10 days or after rain. Other diseases (such as late blight, Septoria leaf spot, and gray leaf spot) can be controlled by these biofungicides and fungicides, so application is multi-purpose.(Garden sprayers are available at Garden.com and Gardens Alive!, along with a good selection of sprayers at Amazon.com.)

How do you prevent early blight?

• Rotate crops. Early blight remains active for a year. Spores can be dormant in the soil for several years.
• Plant disease-resistant hybrids to strengthen your plant’s chances of being blight-free.
• Plant tomatoes in a raised bed to improve drainage and prevent diseases from spreading.
• Give tomato plants extra space (more than 24 inches) to let air to move among leaves and keep them dry.
• Water the soil – not the plants – to prevent splashing. Avoid overhead watering.
• Mulch with black plastic or landscape fabric to prevent fungus from spreading up onto leaves.
• Stake tomato plants for better circulation.
• Remove and destroy affected plants at the end of the season.

Seismic Zons of India

Posted on May 1, 2015

Bureau of Indian Standards [IS-1893 – part – 1: 2002], based on various scientific inputs from a number of agencies including earthquake data supplied by IMD (Indian Meteorological Department, Pune, Maharashtra), has grouped the country into four seismic zones viz., Zone-II, -III, -IV and -V. Of these, zone V is rated as the most seismically prone region, while zone II is the least.

The Modified Mercalli (MM) intensity, which measures the impact of the earthquakes on the surface of the earth, broadly associated with various zones, is as follows:seismicity_map

Horticultural Crops: Area Production and Productivity

Posted on April 30, 2015

The area under horticulture crops which was 12.77 million hectares during 1991-1992 has increased to 23.69 million hectares during 2012-13. The total production during this period has increased by nearly 2.8 times and corresponding productivity has increased 1.5 times.
As compared to 257.1 Million Tonnes of food grain production during 2012-13, the total horticulture production was 268.9 Million Tonnes. The annual growth rates for area and production of horticulture crops during 2012-13 over 2011-12 were 1.9% and 4.5% respectively. Percentage share of vegetables production in the total horticulture production was highest (60.3 % during 2012-13) as compared to other horticulture crops.
The total horticulture production was highest in case of West Bengal (292 lakh MT) followed by Andhra Pradesh (289.13 lakh MT).During 2012-13, the highest production of fruits of 139.39 lakh MT was recorded in Andhra Pradesh (17.1% share) followed by 97.85 lakh MT in Maharashtra (12%). Likewise, the highest production of vegetables (15.7%) was in West Bengal followed by 12.1% in Uttar Pradesh.

Radiocarbon Dating: how does it work??

Posted on April 28, 2015 Updated on April 28, 2015

Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method of determining the age of an object containing organic material by using the properties of radiocarbon (14C), a radioactive isotope of carbon. The method was invented by Willard Libby in the late 1940s, for which he got Nobel Prize for his work in 1960. Radiocarbon dating has now become a standard tool for archaeologists.

The radiocarbon dating method is based on the fact that radiocarbon is constantly being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen. The resulting radiocarbon combines with atmospheric oxygen to form radioactive carbon dioxide, which is incorporated into plants by photosynthesis; animals then acquire 14C by eating the plants. Thus, during its life, a plant or animal is continuously exchanging carbon with its surroundings, and the carbon it contains will have the same proportion of 14C as the atmosphere. When the animal or plant dies, it stops exchanging carbon with its environment, and from that point onwards the amount of 14C it contains begins to reduce as the 14C undergoes radioactive decay thereby gradually decreasing the ratio of 14C to 12C in its remains . Since 14C decays at a known rate,  measuring the amount of 14C in a sample from a dead plant or animal such as piece of wood or a fragment of bone can be used to determine how long it has been since a given sample stopped exchanging carbon from the atmosphere. This information can be used to calculate the time period when the animal or plant died. The older a sample is, the less 14C there is to be detected, and because the half-life of 14C (the period of time after which half of a given sample will have decayed) is about 5,730 years, the oldest dates that can be reliably measured by radiocarbon dating are around 50,000 years ago.