Hi san ahuja,
Thanks for visiting Apple Support Communities.
If the camera on your iPhone is not working, try these troubleshooting steps first:
- If the screen shows a closed lens or black image, force quit the Camera app.
- Ensure the camera lens is clean and free from any obstructions. Use a microfiber polishing cloth to clean the lens.
- Cases can interfere with the camera and the flash. Try gently cleaning the lens with a clean dry cloth or removing the case if you see image or color-quality issues with photos.
- Try turning iPhone off and then back on.
You can find these steps and more information here:
iPhone: Hardware troubleshooting
http://support.apple.com/kb/TS2802
If the issue persists, back up the data on your iPhone and restore your iOS software next:
iOS: Back up and restore your iOS device with iCloud or iTunes
http://support.apple.com/kb/HT1766
Use iTunes to restore your iOS device to factory settings
http://support.apple.com/kb/HT1414
Best,
Jeremy