Rutherford's α-rays Scattering Experiment | Chemistry Class 11

Notes | Chemistry
Rutherford's α-rays  Scattering Experiment - Observation, Nuclear Model of Atom and Limitation.
Class: 11

Rutherford’s model of atom is based on the α-rays scattering experiment which was performed by Ernest Rutherford and his co-workers in 1910 AD. In this experiment α-rays emitted from radioactive substance where bombarded on a thin gold foil around which a movable screen coated with Zns flashes were produced which could be easily observed. By examining the Zns screen in different position, it was possible to determine the proportion of α-rays scattering away from the Gold foil.

Reproduction in Bacteria | Kingdom Monera Biology Class 11

Biology | Zoology
Reproduction in Bacteria | Kingdom Monera
Class : 11

Bacteria usually reproduce by asexual method. 

Binary fission 

The nuclear material becomes enlarged and divides into two parts. Constriction is made in the middle of the cell on the cell membrane dividing cytoplasm into two parts. Ultimately, a cell is divided into two daughter cells. This method is very common and simplest method of reproduction in bacteria. By this method, about 2500,000 bacterial cells are produced in an hour.

Economic Importance of Bacteria | Kingdom Monera - Biology Class 11

Zoology | Biology
Economic Importance of Bacteria - Kingdom Monera
Class : 11

Beneficial Activities 

In Agriculture, the bacteria are mostly important for following reasons 

1. Nitrogen fixation 

Plants cannot trap nitrogen from the atmosphere but bacteria can fix nitrogen and change it into nitrogenous compounds. The phenomenon is called nitrogen fixation. The bacteria, which fix atmospheric nitrogen, are called nitrogen-fixing bacteria.

Cyanobacteria - General Characters, Reproduction and Description of Nostoc

Botany | Biology
General Characters and Reproduction in Cyanobacteria and Description of Nostoc
Class : 11

Cyanobacteria 

General Characters 

· Mostly cyaobacteria are aquatic and some are terrestrial. 

· The organisms are prokaryotic. They may be unicellular, colonial. 

· Cell wall is composed of cellulose. 

· Flagella are absent. Mesosomes are absent like bacteria.

Bryophyta - Its Gametophytic and Sporophytic Generation

Botany | Biology
Bryophyta - Its Gametophytic and Sporophytic Generation
Class: 11

Bryophyta 

They include 960 genera and 24000 species. They grow in moist and shady places and some are aquatic. Plant body does not bear vascular tissues and not differentiated into root shoot and leaves. They show alternation of generation that is in the life cycle two forms of the plant body are produced.

Acoustic Phenomena - 17+ Short Questions With Answer | Physics Class 12

Physics | Wave Motion
Short Questions with Answer from Acoustic Phenomena
Class: 12

1. How are beats produced? What is beat frequency?

Ans. When two sound waves of nearly the same frequency are travelling in the same medium in the same direction, the intensity of the resultant sound rises and falls regularly a number of times a second. These periodic variations in the intensity of sound due to superposition of two sound waves of slightly different frequencies are called beats and hence in this way they are formed. The number of beats heard per second is called beat frequency.

Marchantia - General Description of Structure and Reproduction Process | Biology Class 11

Botany | Biology

Marchantia : General Description of Structure and Reproduction Process

Class: 11

Marchantia 

It is one of the important species of Liverworts. It is widely distributed, commonly found in moist and shady places. There are about 65 species of marchantia. In Nepal there are three species found Marchantia palmate, M. nepalensis, M. polymorpha.

Waves in Pipes and String - 15+ Short Questions With Answer | Physics Class 12

Short Question Answer | Physics
Short Questions-Answer from Waves in Pipes and Strings
Class: 12

1)The frequency of fundamental note of an open organ pipe is double than for closed pipe of same length .Why?

When an air column in an organ pipe is set into vibration, the air column must vibrate with an anti node in case of open organ pipe and a node in case of closed organ pipe. The ends of open organ pipe are antinodes and middle point is node in the fundamental note. If l be the length of pipe and λ0 be the wavelength, then  l =λ0/2 or λ0=2l

Old Question Paper 2070 - Physics Class 12 | Download

Question Paper | Science
Old Question Paper of Physics
Class : 12
Year : 2070 B.S. (2013)

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Digestive System of Earthworm (Pheritima posthuma) | Biology Class 11

Zoology | Notes

Digestive System of Earthworm (Pheritima posthuma)
Class : 11

The process of ingestion, digestion, absorption, and excretion is called digestion. The digestive system is divided into following heads. 

Alimentary Canal: The alimentary canal is long tube, which starts from mouth and ends to anus. 

Mouth: Mouth is small cresentric aperture. It is situated below prostomium at first segment. 

Buccal Cavity: It is thin walled, short tube behind mouth, which extends upto 3rd segment. It helps to ingest food.

Wave Motion - Short Questions With Answer | Physics Class 12

Short Answer Question | Physics
Short Question-Answer form Wave Motion
Class: 12

1. Differentiate between forced vibration and free vibration.

The free vibration and forced vibration can be differentiated by the following points: A body is said to execute free vibration when it is vibrating by itself, while a body is said to execute forced vibration, when it is compelled to vibrate by a periodic force at a frequency other then its natural frequency. A body in free vibration vibrates with its natural frequency while in forced vibration it vibrates with the frequency of the source. A body in free vibration vibrates with the help of internal elastic forces while in forced vibration it vibrates with the help of external periodic force. Free vibration is self-sustained vibration while forced vibration while forced vibration is externally sustained vibration.

Mechanical Waves - Short Questions With Answer | Physics Class 12

Short Answer Question | Physics
Short Question-Answer from Mechanical Waves
Class: 12

1. Why sound made at a distance can be heard distinctly at night than in the day time?

Ans. At night, the atmospheric air becomes more moist than at the day time, which reduces the density of air in the night time. As it is known, the velocity of sound is inversely proportional to the square root of the density (i.e. vs 1/ρ). So, at night velocity of sound is more at night than at day due to reduced density of air. Apart from this, the sound absorbing bodies such as people, vehicles and noise from other sound producing bodies are least at night time as compared to the day time. So sound made at a distance can be heard more distinctly at night than at the day time.

25+ MCQs of AFU / IAAS (BSc. Ag / Forestry) Entrance Exam Question Model with Answer

MCQ | Entrance Exam
25+ MCQs of Entrance Exam with Answer
From : Botany
For:  BSc.Ag / Forestry
Model: AFU /  IAAS

1.Arrangement of microtubules in cilia/flagella from centre to periphery is 

a) 9+2      b) 2+9     c) 0+9       d) 9+0 

Ans: b