## Thursday, 29 September 2022

### REET 2022 RESULTS DECLARED CHECK REET Leve 1, Level 2 2022 RESULT ON reetbser2022.in

REET Result 2022 Declared. REET 2022 exam held on 23.07.2022 and 24.07.2022

Check Result : Click Here to View

## Friday, 23 September 2022

### What is mirror, types of mirror and mirror formula class 10th science numerical

What is mirror?

A mirror is a reflective surface that bounces off light, producing either a real image or a virtual image.

Types of mirror

Mirrors are mainly three types are plane mirrors and concave and convex mirrors.

Concave mirror :-  If the inner side of the spherical mirror is reflecting, it is called a concave mirror.

Convex Mirror : If the outer side of the spherical mirror is reflecting, it is called a convex mirror.

Characteristics of the image formed by a plane mirror.

(i) The Image is erect.

(ii) The Image is of the same size as that of the object.

(iii) The image is laterally inverted. Right side appears to be left and left side appeared to be right.

(iv) The image is virtual.

## Thursday, 22 September 2022

### Reflection and refraction of light lens formula Class 10th science Numerical

Lens :- A transparent material bound by two surfaces, of which one or both surfaces are spherical is called the lens.

There are two types of lenses:

i. Convex (Converging) lens- Convex lenses are thick in the middle and thinner at the edges. A convex lens is also known as the converging lens because it converges parallel light rays inwards to a point known as the focal point.

ii. Concave (Diverging) lens- Concave lenses are flat in the middle and thicker at the edges. The concave lens is also known as a diverging lens because it diverges the parallel light rays outward from a point knows as the focal point.

Lens formula:

If u = object distance, v = image distance and

f = focal length of lens,then the lens formula is given by According to sign conventions we need to assume the distance as follows,

Object distance, u= -ve , Image distance, v = -ve/+ve (depends upon the position of image) and Focal length, f= -ve for concave lens/+ve for convex lens.

Let’s consider following example to understand this formula more precisely.

Ex.1) An object is kept in front of converging lens of focal length 20 cm at distance of 10 cm. Find position of image, nature of image.

Solution: Data given ;( using all sign conventions)

Focal length, f= +20 cm

Object distance, u= -10 cm

Image distance=?

Formula: On substituting the above values, we get ∴ 1/v = 3/20

∴ v = 20/3

∴ v = 6.67 cm

Positive value of ‘v’ indicates that image is real but inverted.

Magnification by lenses (M):

Magnification is defined as the ratio of height of image (h2) to the height of object (h1) or the ratio of image distance (v) to object distance (u). Ex.2) An object of height 5 cm kept in front of convex lens of focal length 25 cm at distance of 10 cm. Find position of image, nature of image and height of the image.

Solution: Data given ;( using all sign conventions)

Height of object, h1= + 5 cm

Focal length, f= +25 cm

Object distance, u= -10 cm

Image distance=?

Image height=?

Formula: ∴ 1/v = 35/200

v = 200/35

∴ v = 5.7 cm

Positive value of ‘v’ indicates that image is real but inverted.

Now to calculate height of image use 2nd formula Hence the height of image obtain here will be 2.85 cm.

(3) The distance of object is 20cm from convex mirror of focal length is 25 cm. Find the position of image?

Given:

F = 15 => convex mirror

Object distance u = -20 cm

Image distance (v) =?

1/f = 1/v + 1/u

1/25 = 1/v + 1/-20

1/25 + 1/20 = 1/v

45/500 = 1/v

V = 500/45 = 11.11

V = 11.1100

The value of  V is +ve so image is virtual.

(4) The radius of curvature is 38 cm. Find the focal length of convex mirror?

Given:

R = 38 cm

Focal length is equal to half of radius of curvature

Focal length = R/2

= 28/2

F = 19 cm

Focal length is 19 cm

(5) Find the position of image if the focal length of convex lens (f) is 8 cm and object is placed 16 cm from lens.

Given:

f = 8 cm

u = – 16 cm

v =?

1/f = 1/v – 1/u

1/8 = 1/v – 1/16

1/v = 1/8 – 1/16

1/v = 1/16

V = 16 cm

∴ The image is placed 16 cm from the principal axis.

## Chemical Names and Common Name of Chemical Formulaरासायनिक सूत्रो के रासायनिक नाम व सामान्य नाम

 सामान्‍य नाम रासायनिक यौगिक रासायनिक सूत्र ब्लीचिंग पाउडर कैल्शियम ऑक्‍सीक्‍लोराइड CaOCL2 चाक (संगमरमर) कैल्शियम कार्बोनेट CaCo3 बेकिंग पाउडर सोडियम बाइकार्बोनेट NaHCO3 पोटाश एलम पोटेशियम एल्युमिनियम सल्फेट KAl(SO₄)₂·12H₂O नीला थोथा कॉपर सल्फेट CuSO4.xH2O बुझा चूना कैल्शियम हाइड्रॉक्साइड Ca(OH)2 त्वरित चूने कैल्शियम ऑक्साइड CaO क्लोरोफॉर्म ट्राइक्‍लोरो मीथेन CHCl3 कास्टिक सोडा सोडियम हाइड्रॉक्‍साइड NaOH कास्टिक पोटाश पोटेशियम हाइड्रॉक्‍साइड KOH शुष्‍क बर्फ ठोस कार्बन डाइ आक्‍साइड CO2 सिरका एसिटिक एसिड CH3COOH धावन सोडा सोडियम कार्बोनेट Na2CO3 प्लास्टर ऑफ पेरिस कैल्शियम सल्फेट CaSO4. 1/2 H2O एप्‍सम मैग्नीशियम सल्फेट MgSo4 जिप्सम कैल्शियम सल्फेट CaSo4. 2H2O भारी जल ड्यूटेरियम ऑक्साइड D2O हरा थोथा फेरस सल्फेट FeSo4 मोहर लवण अमोनियम फेरस सल्फेट (NH4)2Fe(SO4)2·6H2O सफेद थोथा जिंक सल्फेट ZnSo4.7H2O मार्श गैस मीथेन CH4 रेत सिलिकॉन ऑक्साइड SiO2 मैग्नीशिया मैग्नीशियम ऑक्साइड MgO हँसाने वाली गैस नाइट्रस ऑक्साइड N2O वरमेलियम मरक्‍यूरिक सल्फाइड HgS चीनी सुक्रोज C12H22O11 T.N.T. ट्राइनाइट्रो टाइलून C7H5N3O6

## Wednesday, 21 September 2022

### भारत में शास्त्रीय भाषाओं को शास्त्रीय भाषा का दर्जा प्रदान किया गया

भारत में शास्त्रीय भाषाएँ

वर्तमान में छ: भाषाओं को वर्ष 2004- 2014 तक शास्त्रीय भाषा का दर्जा प्रदान किया गया जो इस प्रकार हैं-

• तमिल (2004)
• संस्कृत (2005)
• कन्नड़ (2008)
• तेलुगू (2008)
• मलयालम (2013)
• ओडिया (2014)

### REET 2022 RESULTS DECLARED CHECK REET Leve 1, Level 2 2022 RESULT ON reetbser2022.in

REET Result 2022 Declared. REET 2022 exam held on 23.07.2022 and 24.07.2022 Check Result : Click Here to View