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(C) White pellets/flakes

Periscope is an instrument used in submarines to see the objects or persons above the water level.

The mirrors which are the parts of spheres are called spherical mirrors.

Spherical mirrors are of two types : 

1. Convex mirrors (Reflecting surface bent outward) 

2. Concave mirrors (Reflecting surface bent inward)

A concave mirror forms real and virtual images, erect and inverted images, smaller, same size and bigger images depending on the position of object in front of it.

Convex Mirrors are used as Rear-view mirrors and also used at the junctions of roads.

Formula for number of images formed between two mirrors .

Number of images (n) = 360°/θ -1, where 0 is the angle between the mirrors.

• Concave mirrors are used by ENT doctors as Head Mirrors,
• Dentists also use concave mirrors to get a bigger image of the teeth.
• Eye specialist using a special instrument called Ophthalmoscope. It is fitted with a concave mirror having a small hole near its center.
• The surface of reflection in a torch light or the headlights of vehicles is concave.

(c) Rs 222

S.P. = Rs 178, Loss = 11%

\(\therefore\) C.P = \(\frac{178\times100}{(100-11)}\) =  \(\frac{178\times100}{89}\) = 200

Now C.P. = Rs 200, Profit = 11%

\(\therefore\) S.P = \(\frac{200\times111}{100}\) = Rs 222.

(c) 21%

C.P. of 11 articles = Rs 10

C.P. of 1 article = Rs \(\frac{10}{11}\)

S.P. of 10 articles = Rs 11

\(\Rightarrow\) S.P. of 1 article = Rs \(\frac{11}{10}\)

\(\therefore\) Profit % = \(\frac{\frac{11}{10}-\frac{10}{11}}{\frac{10}{11}}\)x 100 = \(\frac{\frac{121-100}{110}}{\frac{10}{11}}\)x 100

= \(\frac{21\times11}{110\times10}\) x 100 = 21%

Carbon and its compounds on burning in air or oxygen release a large amount of heat and light. Hence, carbon and its compounds are used as fuels for most applications.

Soap is a salt of a strong base (NaOH or KOH) and a weak acid (carboxylic acid). So, its aqueous solution is basic in nature. Hence, an aqueous solution of soap will turn red litmus paper blue.

The distance of the object from the mirror is called Object distance.

The distance of the image from the mirror is called Image distance.

Images are not clear or sometimes cannot form the images at all in case of irregular reflection.

Dispersion : Splitting of white light into seven colours is called Dispersion.

Safe browsing : Opening of authorized websites in computers is called safe browsing.

The Light rays that fall on the objects are called incident rays. The light rays that bounce back from the objects are called reflected rays.

Normal : Perpendicular line to the surface of the mirror at incident point is called normal to the surface.

Reflection from a smooth and shiny surface is called regular reflection.

Incident ray : The light rays that fall on the objects are called incident rays.

Clear images are formed in case of regular reflection.

Reflection from an irregular or uneven surface is called irregular reflection or diffused reflection.

Manmade sources of light : Sources which need the human involvement to release light energy are called manmade sources of light.

Angle of incidence (I) : The angle made by incident ray with the normal is called angle of incidence (i).

The poet presents winter as the sign of death because everything becomes still during winter but as soon as the spring season sets in new leaves and flowers bloom everywhere and it is the sign of new life after death so that we should not give up hope. and always remain busy in our work.

कवि सर्दी को मृत्यु के प्रतीक के रूप में दर्शाता है क्योंकि सर्दी के मौसम में प्रत्येक चीज स्थिर हो जाती है। लेकिन जैसे ही बसन्त ऋतु आती है तो चारों तरफ नई पत्तियाँ तथा फूल खिल जाते हैं और यह नए जीवन का प्रतीक है। इसलिए हमें आशा नहीं छोड़नी चाहिए और हमें सदैव अपने कार्य में व्यस्त रहना चाहिए।

This bundle of light rays are called beam of light rays. 

These are three types : 

1. Parallel beam of light rays 

2. Converging beam of light rays 

3. Diverging beam of light rays.

Light is not a single ray, but a bundle of rays. 

Ex : bulb, torch light, candle.

“Light rays which travel from different directions to meet at a point are called as Con-verging beam of light rays”.

“Light rays which travel from a source moving in different directions are called as Diverging beam of light rays.”

A business unit should inform its suppliers well in advance about the products/services it will require. Doing so will help the business to obtain a constant supply which can then be used to process and put in market on time and in continuity. This also improves credit of business in the market in the sense that it supplies products to customers whenever they need.

Malav lake is situated at Dholka.

Rani-vi-Vav is located at Patan.

The terracing of land and construction of bunds to check the flow of water, the practice of contour cultivation and the planting of appropriate types of vegetation are few measures to check erosion.

The prevention of soil erosion would help to conserve and keep the water where it is wanted, in other words, on and in the soil. Thus it serves a double purpose.

सही विकल्प है (अ) आयास और भार के मध्य आलम्ब होता है।

झाडू तृतीय प्रकार का उत्तोलक है, सरौता द्वितीय प्रकार का उत्तोलक है, जबकि कैंची प्रथम प्रकार का उत्तोलक है।

ऐसे साधन जो कार्य को सरलता, सुविधा और तेजी से करने में सहायक होते हैं, सरल मशीन कहलाते हैं।

दैनिक जीवन में घर्षण बल का अत्यधिक महत्व है। घर्षण बल के कारण ही लोगों का चलना, दौड़ना, उठना, बैठना आदि क्रियाएँ संभव होती हैं। पेंसिल तथा कागज के बीच घर्षण बल के कारण ही लिखना संभव हो पाता है। माचिस की तीली को जब माचिस की सतह पर रगड़ा जाता है तो घर्षण बल के कारण ही वह जलती है। मोटरकार, बस तथा अन्य वाहनों के पहियों तथा सड़क की सतह के मध्य घर्षण बल लगने कारण ही उनका चलना संभव हो पाता है। दाँतेदार भारी तथा लकड़ी के बीच घर्षण बल के द्वारा ही लकड़ी को काट कर विचित्र आकृतियाँ बनाते हैं।

बल दो प्रकार के होते हैं- 1. सम्पर्क बल और 2. असम्पर्क बल।
टूथपेस्ट की ट्यूब को दबाने पर टूथपेस्ट का निकलना सम्पर्क बले का उदाहरण है। चुंबकीय सुई में विक्षेप होना असम्पर्क बल के कारण होता है क्योंकि चुम्बक के निकट अलग-अलग स्थान पर चुम्बकीय सुर्ह की दिशा में परिवर्तन बिना प्रत्यक्ष सम्पर्क के होता है।

(क) पृथ्वी द्वारा किसी वस्तु पर लगाये गये बल को गुरूत्व बले कहते हैं।
(ख) सम्पर्क सतहों, तलों के बीच लगने वाला बल घर्षण बल है।
(ग) लोहे की कीलें चुंबकीय बल के कारण चुम्बक पर चिपकती हैं।
(घ) सरौता द्वितीय श्रेणी का उत्तोलक है।
(ङ) घिरनी बल की मात्रा में परिवर्तन कर देती है।

सही विकल्प है (स) गुरुत्व बल

सही विकल्प है (द) कुएँ से पानी खींचना

सही विकल्प है (द) उपर्युक्त सभी पर

सही विकल्प है (स) पाँच प्रकार की

(A) 3247.62 km 

The moon’s distance from the earth is 360000 kms and its diameter subtends an angle of 31' at the eye of observer, then the diameter of the moon is 3247.62 km 

(C)  \(\frac{\pi}5\) radian

A circular wire of diameter 10 cm is cut and placed along the circumference of a circle of diameter 1 metre. The angle subtended by the wire at the centre of the circle is equal to \(\frac{\pi}5\) radian

Correct option is: (d) concave, convex