Submitted by Editor
Acknowledgment
I am grateful to Almighty for giving me the strength to successfully conduct my experiment and for sustaining my efforts which many a times did oscillate.
I am deeply indebted to Mr. O.J. Abraham sir, our physics faculty without whose constructive guidance this project/venture would not have been a success. His valuable advice and suggestions for the corrections, modifications and improvement did enhance the perfection in performing my job well.
I am obliged to Sr. Kiran our principal for providing the best of facilities and environment to bring out our innovation and spirit of inquiry through this venture.
I take special pleasure in acknowledging Mam Nirmala for her willingness in providing us with necessary lab equipments and constant support without which this effort would have been worthless.
I am grateful to My Parents and My Brother whose blessings and wishes have gone a long way in the completion of this arduous task.
Last but not the least I thank all My Friends and Batch Mates, without their prompt support my efforts would have been in vain.
SAUMYA GUPTA CERTIFICATE
THIS IS TO CERTIFY THAT MISS SAUMYA GUPTA OF CLASS XII-SC HAS SCCESSFULLY CARRIED OUT THE PROJCT ENTITLED “ANALYSIS ON FERTILIZERS” UNDER MY SUPERVISION.
ALL THE WORKS RELATED TO THE THESIS WAS DONE BY THE CANDIDATE HERSELF.
THE APPROACH TOWARDS THE SUBJECT HAS BEEN SINCERE AND SCIENTIFIC.
MRS.BEENA DASHORA
CHEMISTRY FACULTY
ST.MARY’S CONVENT SENIOR
SECONDARY SCHOOL
INDEX
1. INTRODUCTION
(a) Definition
(b) Laws of refraction
(c) Refractive index
(d) Snell’s law
(e) Mathematical relations
(f) Phenomenon
(g) Total internal reflection
2. EXPERIMENT:
(a) Aim
(b) Apparatus
(c) Procedure
(d) Results
(e) Precautions
3. BIBLIOGRAPHY
INTRODUCTION
(a) Definition: When light travels from one medium to another it changes the direction of its path at the interface of the two media.
It is bending of a wave when it enters a medium where its speed is different.
(b) Laws of refraction:
(i) The incident ray, the refracted ray and the normal to the interface at the point of incidence, all lie in the same plane.
(ii) The ratio of the sine of the angle of incidence of the sine of angle of refraction is constant.
Bending Light:
When a stick is submerged into water, the stick appears bent at the point it enters into water. This optical effect is due to refraction. As light passes from one transparent medium to another, it changes speed and it bends. How much this happens depends on the refractive index and the angle between the light ray and the line perpendicular i.e. normal to the surface separating the two mediums.
INDEX OF REFRACTION OR REFRACTIVE INDEX:
It is defined as the speed of light in vacuum divided by the speed of light in the medium.
It is represented by “µ” or “n”
µ = C/V
C – Speed of light in vacuum
V – Speed of light in medium
It is also the degree or extent of deviation from its original path.
A ray of light travels along straight line in a homogenous medium meaning density same throughout. When it travels from one medium to another medium of different densities the light deviates from its original path. The amount of deviation of light from its original path depends on the indices of refraction of the two media and is described quantitatively by Snell’s law.
Diagram showing Refraction. DEFINITIONS:
1. Angle of incidence – The angle that the incident ray makes with the normal is known as angle of incidence (“i").
Ð i = Ð AOB
AO – Incident ray
OB – Normal
2. Angle of refraction – The angle that the refracted ray makes with the normal is known as angle of refraction.
Ð r = Ð COQ
OQ – Refracted ray,
OC – Normal
3. Angle of emergence – The angle that the emergent ray makes with the normal is known as reemergence.
Ð e = Ð SQR
SQ – Emergent ray
RS – Normal
Common Refractive Index:
The values given are appropriate and do not account for the small variation of index with light wavelength which is called dispersion.
Table for refractive indices
Medium | Refractive index | Medium | Refractive index |
1. Vacuum | 1.000 | 7. Ethyl alcohol | 1.362 |
2. Air | 1.000277 | 8. Glycerin | 1.473 |
3. Water | 1.33 | 9. Ice | 1.310 |
4. Carbon disulphide | 1.63 | 10. Polystrene | 1.59 |
5. Methylene iodide | 1.74 | 11. Crown glass | 1.50-1.62 |
6. Diamond | 2.417 | 12. Flint glass | 1.57-1.75 |
Snell’s Law:
In 1621, a Dutch physicist named Willeboard Snell (1591-1626), derived the relationship between the different angles of light as it passes from one transparent medium to another. Snell’s law states that when light passes from one transparent medium to another speed of light changes and thus it deviates from its original path and extent of deviation is given by the relation-
n1 sin q1 = n2 sin q2
n1= Refractive index of medium 1
n2 = Refractive index of medium 2
q1 = angle of incidence in medium 1
q2 = angle of refraction in medium
CASE I
Since n1 < n2
Therefore medium 1 is rarer than medium 2
Therefore the relation
n1/ n2 = sin q2 / sin q1
n1/n2 is less than 1
sin q1 / sin q2 < 1
sin q1 > sin q2
Since 0 < q < p / 2 (when sin q1> sin q2)
q1 > q2
Therefore refracted ray bends towards the normal when it travels from rarer to dense medium.
Case II :
Since n1> n2
Therefore by the relation
n1 / n2 = sin q2 / sin q1
Therefore n1> n2
n1/ n2 > 1
à sin q2 / sin q1 > 1
à sin q2 > sin q1
{When 0 < q < p / 2 }
q2 > q1
Therefore refracted ray bends away from the normal when it travels from denser to rarer medium.(For both cases refer to diagrams)
OTHER MATHEMATICAL RELATIONS FOR µ :
1. Frequency is the characteristics of the source and remains unaffected when the medium changes.
Let there be two mediums 1 and 2
V1= be the velocity of light in medium 1
V2 = be the velocity of light in medium 2
l1 = wavelength in medium 1
l2 = wavelength in medium 2
V1 = nl1
V2 = nl2
V1 / V2 = l1 / l2
2. Refractive index of medium 1 with respect to 2 = n12
n12= V2 / V1 it is the ratio of velocity of light in medium 2 with respect to medium 1.
3. Refractive index of medium 1 with respect to medium 2
Medium 1 = water
Medium 2 = air
Air w.r.t. water wµa = Apparent depth / Actual depth
Water w.r.t to air aµw = Actual depth / Apparent depth
Refer to diagram
PHENOMENON DUE TO ATMOSPHERIC REFRACTION:
TOTAL INTERNAL REFLECTION:
When light passes from an optically denser medium to a rarer medium at the interface, it is partly reflected back into the same medium and partly refracted into the second medium. This reflection is called internal reflection.
When a ray of light travels from denser to rarer medium the ray deviate away from the normal. At a particular angle called critical angle the refracted ray just grazes or touches the surface i.e. Le of refraction = 90°. The angle of refraction in denser medium for which the Le of refraction in rarer medium = 90° is called critical angle.
If angle of incidence is greater than the critical angle the ray gets totally internally reflected.
RELATION BETWEEN REFRACTIVE INDEX AND CRITICAL ANGLE:
Consider that ray of light is traveling from denser to rarer medium. Let ‘C’ be the critical angle. The angle of incidence (i)
Ð i = LC
Since angle of refraction = 90°
Refractive index of air w.r.t medium is = sin i / sin r
mµa = Sin C / sin 90°
mµa = Sin C
Sin C = 1 / aµm
DIAGRAM
SOME PHENOMENON DUE TO TOTAL INTERNAL REFLECTION:
EXPERIMENT
Aim: To determine refractive index of water using a traveling microscope.
Apparatus: A coin, a beaker, paper piece, traveling microscope.
Theory and Formula used:
Refraction is a phenomenon of propagation of light from one transparent medium into the other medium such that light deviate from its original path. The ratio of velocity of light in the first medium to that in the second medium is called refractive index of second medium w.r.t. the first medium.
The bottom surface of a vessel containing a refracting liquid appears to be raised, such that apparent depth is less than the real depth. Refractive index of refracting liquid is defined as the ratio of real depth to the apparent depth.
µ = Real depth / Apparent depth
If reading of real depth of the coin = r1
With water = r2
Paper piece = r3
Real depth = r3 – r1
Apparent depth = r3 – r2
µ = r3 – r1 / r3 – r2
Refer to the diagram
PROCEDURE:
OBSERVATIONS
Least count of traveling microscope:
10 vernier scale division = 9 main scale division
50 V.S.D. = 49 M.S.D.
1 V.S.D. = 49/50 M.S.D.
L.C. = 1 M.S.D. – 1 V.S.D.
= 1/50 M.S.D.
M.S.D. = 1/20 cm = 0.05 cm
L.C. = 1/50 x 0.05 = 0.001 cm
CALCULATIONS
RESULTS
The refractive index of water by using traveling microscope is determined to be 1.33.
PRECAUTIONS
ELEMENTS
NITROGEN:
Major fertilizers containing N:
(a) Ammonium nitrate (NH4NO3)
(b) Potassium nitrate (KNO3)
(c) Urea (NH2CONH2)
(d) Ammonium sulphate [(NH4)2SO4]
Preparation:
Most of nitrogen fertilizers are obtained form synthetic NH3. This chemical compound is used as gas or in water solution or it is converted to salts.
Nitrogen Deficiencies
(a) Pale, green, yellow leaves
(b) Stunted growth
Nitrogen in Excess –
(a) Lower disease resistance
(b) Weaken stem
(c) Decay maturity
(d) Lower fruit quality
PHOSPHORUS:
Major fertilizers containing P:
(a)DAP – Diammonium phosphate [(NH4)2PO4]
(b)Ca3(PO4)2 – Calcium phosphate
(c)Triple phosphate and super phosphate
Preparation:
Most phosphoric fertilizers are obtained by the treatment of calcium phosphate with H2SO4and phosphoric fertilizers. Calcium phosphate is mainly derived from phosphate rock and bones. Phosphate rock is found in deposits of sedimentary origin laid down on beds of ocean floor.
Phosphorus deficiencies –
(a) Pale purple colour on the underside of leaves
(b) Reduced flower, fruits and seed production
Advantages of P:
Phosphorous in excess
POTASSIUM:
Major fertilizers containining K:
Preparation:
It is the seventh most abundant element found in earth’s crust. Potassium chloride which is principal commercial form of potash and some KNO3 is also used for production of potash fertilizer.
Potassium deficiencies:
Advantages of K:
Potassium in excess
Fertilisers- V
Experiment | Observation | Inference | |
1. | Take a pinch of fertilizer + few drops of dil. H2SO4 | No reaction | Dil. group absent |
2. | Take a pinch of fertilizer + few drops of conc. H2SO4 | No reaction | Conc. group absent |
3. | Take 1 ml of soda extract and acidify it with dil HCl. Add few drops of BaCl2 soln. to it. | No reaction | Volatile group absent |
4. | A pinch of fertilizer + few drops of NaOH soln. Heat it. | No reaction | Zero group absent |
5. | Take 1 ml of O.S (original solution)* in a solution and to it add few drops of dil. HCl | No reaction | 1st group absent |
6. | Take 1 ml of O.S (original solution) in a solution, to it add few drops of dil. HCl. Warm the solution, and pass H2S gas. | No reaction | 2nd group absent |
7. | Take 1 ml of O.S (original solution) in a solution and to it add few drops of dil. HCl .add few drops of conc. HNO3.heat it. Cool it. Add a pinch of solid NH4Cl followed by excess of NH4OH. | No reaction | 3rd group absent |
8. | Take 1 ml of O.S (original solution) in a solution and to it add few drops of dil. HCl. Add a pinch of solid NH4Cl followed by excess of NH4OH. Warm the solution and pass H2S gas. | No reaction | IV group absent |
9. | Take 1 ml of OS + few drops of dil. HCl + a pinch of solid NH4Cl + 1 or 2 ml of (NH4)2CO3 | White ppt | V group present, may be Ba2+, Kr2+ or Ca2+ |
10. | Filter the white precipitate, take a part of it, and dissolve it in minimum amount of CH3COOH. Now add (NH4)2C2O4 | White ppt | Ca2+ confirmed. |
11. | Flame test | Brick red flame | Ca2+ confirmed. |
RESULT- Fertilizer has Ca2+as cation. (The fertilizer detected is Vermi Compost).
*****
Fertilizer–III
Experiment | Observation | Inference | |
1. | Take 1 ml of Lassaigne Solution (L.S.)* in a test tube and to it add few drops of freshly prepared ferrous sulphate solution. Heat it. Cool it. Add few drops of conc. H2SO4 | Prussian blue colour | Nitrogen present in elemental form. |
RESULT- The given fertilizer has N in elemental form. (The fertilizer detected is urea).
*****
(Urea)
O.C.N + Na NaCN
FERTILIZER 5(vermi compost)
Ca2+ (aq) + CO32-(aq) CaCO3 (s) + 2CH3COOH
2CH3COOH + CaCO3 Ca [CH3COO]2 + H2O +CO2
Ca2+ (aq) +C2O42- CaC2O4(s)
Reading of microscope focused on
Coin without water | Coin with water | Paper in water | |||||||
M.S.R. (M) cm |
V. div coinciding (n) | Reading + n X L.C = r1 |
M.S.R. (M) cm |
V. div coinciding (n) | Reading + n X LC = r2 |
M.S.R. (M) cm |
V. div coinciding n | Reading + nXLC = r3 |
|
1. | 5.2 | 5 | 5.205 | 5.9 | 40 | 5.940 | 8.15 | 12 | 8.162 |
2. | 5.1 | 40 | 5.140 | 5.80 | 39 | 5.839 | 7.95 | 10 | 7.400 |
3. | 5.05 | 20 | 5.070 | 5.75 | 36 | 5.789 | 8.00 | 20 | 8.020 |
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